Invoke rpmh_flush for non OSI targets

Currently rpmh ctrlr dirty flag is set for all cases regardless of data is really changed or not. Add changes to update dirty flag when data is changed to newer values.

Also move dirty flag updates to happen from within cache_lock and remove unnecessary INIT_LIST_HEAD() call and a default case from switch.

Fixes 600513dfeef3 ("drivers: qcom: rpmh: cache sleep/wake state requests")

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
 drivers/soc/qcom/rpmh.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

drivers/soc/qcom/rpmh.c +11 -7

index eb0ded0..f28afe4 100644
@@ -133,26 +133,30 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
 
        req->addr = cmd->addr;
        req->sleep_val = req->wake_val = UINT_MAX;
-       INIT_LIST_HEAD(&req->list);
        list_add_tail(&req->list, &ctrlr->cache);
 
 existing:
        switch (state) {
        case RPMH_ACTIVE_ONLY_STATE:
-               if (req->sleep_val != UINT_MAX)
+               if (req->sleep_val != UINT_MAX) {
                        req->wake_val = cmd->data;
+                       ctrlr->dirty = true;
+               }
                break;
        case RPMH_WAKE_ONLY_STATE:
-               req->wake_val = cmd->data;
+               if (req->wake_val != cmd->data) {
+                       req->wake_val = cmd->data;
+                       ctrlr->dirty = true;
+               }
                break;
        case RPMH_SLEEP_STATE:
-               req->sleep_val = cmd->data;
-               break;
-       default:
+               if (req->sleep_val != cmd->data) {
+                       req->sleep_val = cmd->data;
+                       ctrlr->dirty = true;
+               }
                break;
        }
 
-       ctrlr->dirty = true;
 unlock:
        spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 

Quoted 56 lines · Maulik Shah

Currently rpmh ctrlr dirty flag is set for all cases regardless of data is really changed or not. Add changes to update dirty flag when data is changed to newer values.

Also move dirty flag updates to happen from within cache_lock and remove unnecessary INIT_LIST_HEAD() call and a default case from switch.

Fixes 600513dfeef3 ("drivers: qcom: rpmh: cache sleep/wake state requests")

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
  drivers/soc/qcom/rpmh.c | 21 +++++++++++++--------
  1 file changed, 13 insertions(+), 8 deletions(-)

drivers/soc/qcom/rpmh.c +11 -7

index eb0ded0..f28afe4 100644
@@ -133,26 +133,30 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
 
         req->addr = cmd->addr;
         req->sleep_val = req->wake_val = UINT_MAX;
-       INIT_LIST_HEAD(&req->list);
         list_add_tail(&req->list, &ctrlr->cache);
 
  existing:
         switch (state) {
         case RPMH_ACTIVE_ONLY_STATE:
-               if (req->sleep_val != UINT_MAX)
+               if (req->sleep_val != UINT_MAX) {
                         req->wake_val = cmd->data;
+                       ctrlr->dirty = true;
+               }
                 break;
         case RPMH_WAKE_ONLY_STATE:
-               req->wake_val = cmd->data;
+               if (req->wake_val != cmd->data) {
+                       req->wake_val = cmd->data;
+                       ctrlr->dirty = true;
+               }
                 break;
         case RPMH_SLEEP_STATE:
-               req->sleep_val = cmd->data;
-               break;
-       default:
+               if (req->sleep_val != cmd->data) {
+                       req->sleep_val = cmd->data;
+                       ctrlr->dirty = true;
+               }
                 break;
         }
 
-       ctrlr->dirty = true;
  unlock:
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 

drivers/soc/qcom/rpmh.c static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req) · line 294

Quoted 5 lines

drivers/soc/qcom/rpmh.c +1 -0

@@ -287,6 +291,7 @@ static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
 
         spin_lock_irqsave(&ctrlr->cache_lock, flags);
         list_add_tail(&req->list, &ctrlr->batch_cache);
+       ctrlr->dirty = true;

Is this fixing a case where we were not previously marking the controller dirty but should have?

I notice there's a fixes tag, but it
would be helpful to add something to the commit text indicating that you're fixing a missing case where the controller should have been marked dirty.

With that fixed, you can add my tag:

Reviewed-by Evan Green <[email protected]>

Add changes to invoke rpmh flush() from within cache_lock when the data in cache is dirty.

This is done only if OSI is not supported in PSCI. If OSI is supported rpmh_flush can get invoked when the last cpu going to power collapse deepest low power mode.

Also remove "depends on COMPILE_TEST" for Kconfig option QCOM_RPMH so the driver is only compiled for arm64 which supports psci_has_osi_support() API.

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
 drivers/soc/qcom/Kconfig |  2 +-
 drivers/soc/qcom/rpmh.c  | 33 ++++++++++++++++++++++-----------
 2 files changed, 23 insertions(+), 12 deletions(-)

drivers/soc/qcom/Kconfig +1 -1

index d0a73e7..2e581bc 100644
@@ -105,7 +105,7 @@ config QCOM_RMTFS_MEM
 
 config QCOM_RPMH
        bool "Qualcomm RPM-Hardened (RPMH) Communication"
-       depends on ARCH_QCOM && ARM64 || COMPILE_TEST
+       depends on ARCH_QCOM && ARM64
        help
          Support for communication with the hardened-RPM blocks in
          Qualcomm Technologies Inc (QTI) SoCs. RPMH communication uses an

drivers/soc/qcom/rpmh.c +22 -8

index f28afe4..6a5a60c 100644
@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/psci.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>

@@ -158,6 +159,13 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
        }
 
 unlock:
+       if (ctrlr->dirty && !psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return ERR_PTR(-EINVAL);
+               }
+       }
+
        spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
        return req;

@@ -285,26 +293,35 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
 }
 EXPORT_SYMBOL(rpmh_write);
 
-static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
+static int cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&ctrlr->cache_lock, flags);
+
        list_add_tail(&req->list, &ctrlr->batch_cache);
        ctrlr->dirty = true;
+
+       if (!psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return -EINVAL;
+               }
+       }
+
        spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+
+       return 0;
 }
 
 static int flush_batch(struct rpmh_ctrlr *ctrlr)
 {
        struct batch_cache_req *req;
        const struct rpmh_request *rpm_msg;
-       unsigned long flags;
        int ret = 0;
        int i;
 
        /* Send Sleep/Wake requests to the controller, expect no response */
-       spin_lock_irqsave(&ctrlr->cache_lock, flags);
        list_for_each_entry(req, &ctrlr->batch_cache, list) {
                for (i = 0; i < req->count; i++) {
                        rpm_msg = req->rpm_msgs + i;

@@ -314,7 +331,6 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
                                break;
                }
        }
-       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
        return ret;
 }

@@ -386,10 +402,8 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
                cmd += n[i];
        }
 
-       if (state != RPMH_ACTIVE_ONLY_STATE) {
-               cache_batch(ctrlr, req);
-               return 0;
-       }
+       if (state != RPMH_ACTIVE_ONLY_STATE)
+               return cache_batch(ctrlr, req);
 
        for (i = 0; i < count; i++) {
                struct completion *compl = &compls[i];

drivers/soc/qcom/rpmh.c +0 -1

  */
 int rpmh_flush(struct rpmh_ctrlr *ctrlr)
 {
--

QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

Hi Maulik,
Thanks for spinning this so promptly.

Quoted 118 lines · Maulik Shah

Add changes to invoke rpmh flush() from within cache_lock when the data in cache is dirty.

This is done only if OSI is not supported in PSCI. If OSI is supported rpmh_flush can get invoked when the last cpu going to power collapse deepest low power mode.

Also remove "depends on COMPILE_TEST" for Kconfig option QCOM_RPMH so the driver is only compiled for arm64 which supports psci_has_osi_support() API.

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
  drivers/soc/qcom/Kconfig |  2 +-
  drivers/soc/qcom/rpmh.c  | 33 ++++++++++++++++++++++-----------
  2 files changed, 23 insertions(+), 12 deletions(-)

drivers/soc/qcom/Kconfig +1 -1

index d0a73e7..2e581bc 100644
@@ -105,7 +105,7 @@ config QCOM_RMTFS_MEM
 
  config QCOM_RPMH
         bool "Qualcomm RPM-Hardened (RPMH) Communication"
-       depends on ARCH_QCOM && ARM64 || COMPILE_TEST
+       depends on ARCH_QCOM && ARM64
         help
           Support for communication with the hardened-RPM blocks in
           Qualcomm Technologies Inc (QTI) SoCs. RPMH communication uses an

drivers/soc/qcom/rpmh.c +22 -8

index f28afe4..6a5a60c 100644
@@ -12,6 +12,7 @@
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
+#include <linux/psci.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/types.h>

@@ -158,6 +159,13 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
         }
 
  unlock:
+       if (ctrlr->dirty && !psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return ERR_PTR(-EINVAL);
+               }
+       }
+
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return req;

@@ -285,26 +293,35 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
  }
  EXPORT_SYMBOL(rpmh_write);
 
-static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
+static int cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
  {
         unsigned long flags;
 
         spin_lock_irqsave(&ctrlr->cache_lock, flags);
+
         list_add_tail(&req->list, &ctrlr->batch_cache);
         ctrlr->dirty = true;
+
+       if (!psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return -EINVAL;
+               }
+       }
+
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+
+       return 0;
  }
 
  static int flush_batch(struct rpmh_ctrlr *ctrlr)
  {
         struct batch_cache_req *req;
         const struct rpmh_request *rpm_msg;
-       unsigned long flags;
         int ret = 0;
         int i;
 
         /* Send Sleep/Wake requests to the controller, expect no response */
-       spin_lock_irqsave(&ctrlr->cache_lock, flags);
         list_for_each_entry(req, &ctrlr->batch_cache, list) {
                 for (i = 0; i < req->count; i++) {
                         rpm_msg = req->rpm_msgs + i;

@@ -314,7 +331,6 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
                                 break;
                 }
         }
-       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return ret;
  }

@@ -386,10 +402,8 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
                 cmd += n[i];
         }
 
-       if (state != RPMH_ACTIVE_ONLY_STATE) {
-               cache_batch(ctrlr, req);
-               return 0;
-       }
+       if (state != RPMH_ACTIVE_ONLY_STATE)
+               return cache_batch(ctrlr, req);
 
         for (i = 0; i < count; i++) {
                 struct completion *compl = &compls[i];

drivers/soc/qcom/rpmh.c static int send_single(struct rpmh_ctrlr *ctrlr, enum rpmh_state state, · line 460

Quoted 6 lines

drivers/soc/qcom/rpmh.c +0 -3

@@ -455,9 +469,6 @@ static int send_single(struct rpmh_ctrlr *ctrlr, enum rpmh_state state,
   * Return: -EBUSY if the controller is busy, probably waiting on a response
   * to a RPMH request sent earlier.
   *
- * This function is always called from the sleep code from the last CPU
- * that is powering down the entire system. Since no other RPMH API would be
- * executing at this time, it is safe to run lockless.

Oh nice, I didn't even see that comment. We should probably replace that with a comment indicating that we assume ctrlr->cache_lock is already held.

Please also remove this comment in rpmh_flush():

         /*
          * Nobody else should be calling this function other than system PM,
          * hence we can run without locks.
          */
         list_for_each_entry(p, &ctrlr->cache, list) {

-Evan

Quoted 7 lines

drivers/soc/qcom/rpmh.c +0 -1

   */
  int rpmh_flush(struct rpmh_ctrlr *ctrlr)
  {
--

QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

Add changes to invoke rpmh flush() from within cache_lock when the data in cache is dirty.

This is done only if OSI is not supported in PSCI. If OSI is supported rpmh_flush can get invoked when the last cpu going to power collapse deepest low power mode.

Also remove "depends on COMPILE_TEST" for Kconfig option QCOM_RPMH so the driver is only compiled for arm64 which supports psci_has_osi_support() API.

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
 drivers/soc/qcom/Kconfig |  2 +-
 drivers/soc/qcom/rpmh.c  | 33 ++++++++++++++++++++++-----------
 2 files changed, 23 insertions(+), 12 deletions(-)

drivers/soc/qcom/Kconfig +1 -1

index d0a73e7..2e581bc 100644
@@ -105,7 +105,7 @@ config QCOM_RMTFS_MEM
 
 config QCOM_RPMH
        bool "Qualcomm RPM-Hardened (RPMH) Communication"
-       depends on ARCH_QCOM && ARM64 || COMPILE_TEST
+       depends on ARCH_QCOM && ARM64
        help
          Support for communication with the hardened-RPM blocks in
          Qualcomm Technologies Inc (QTI) SoCs. RPMH communication uses an

drivers/soc/qcom/rpmh.c +1 -0

index f28afe4..6a5a60c 100644
@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/psci.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>

drivers/soc/qcom/rpmh.c +13 -4

+
        spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
        return req;

@@ -285,26 +293,35 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
 }
 EXPORT_SYMBOL(rpmh_write);
 
-static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
+static int cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&ctrlr->cache_lock, flags);
+
        list_add_tail(&req->list, &ctrlr->batch_cache);
        ctrlr->dirty = true;
+
+       if (!psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return -EINVAL;
+               }
+       }
+
        spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+
+       return 0;
 }
 
 static int flush_batch(struct rpmh_ctrlr *ctrlr)
 {
        struct batch_cache_req *req;
        const struct rpmh_request *rpm_msg;
-       unsigned long flags;
        int ret = 0;
        int i;
 
        /* Send Sleep/Wake requests to the controller, expect no response */
-       spin_lock_irqsave(&ctrlr->cache_lock, flags);
        list_for_each_entry(req, &ctrlr->batch_cache, list) {
                for (i = 0; i < req->count; i++) {
                        rpm_msg = req->rpm_msgs + i;

@@ -314,7 +331,6 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
                                break;
                }
        }
-       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
        return ret;
 }

Hi,

Quoted 44 lines · Maulik Shah

Add changes to invoke rpmh flush() from within cache_lock when the data in cache is dirty.

This is done only if OSI is not supported in PSCI. If OSI is supported rpmh_flush can get invoked when the last cpu going to power collapse deepest low power mode.

Also remove "depends on COMPILE_TEST" for Kconfig option QCOM_RPMH so the driver is only compiled for arm64 which supports psci_has_osi_support() API.

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
  drivers/soc/qcom/Kconfig |  2 +-
  drivers/soc/qcom/rpmh.c  | 33 ++++++++++++++++++++++-----------
  2 files changed, 23 insertions(+), 12 deletions(-)

drivers/soc/qcom/Kconfig +1 -1

index d0a73e7..2e581bc 100644
@@ -105,7 +105,7 @@ config QCOM_RMTFS_MEM
 
  config QCOM_RPMH
         bool "Qualcomm RPM-Hardened (RPMH) Communication"
-       depends on ARCH_QCOM && ARM64 || COMPILE_TEST
+       depends on ARCH_QCOM && ARM64
         help
           Support for communication with the hardened-RPM blocks in
           Qualcomm Technologies Inc (QTI) SoCs. RPMH communication uses an

drivers/soc/qcom/rpmh.c +1 -0

index f28afe4..6a5a60c 100644
@@ -12,6 +12,7 @@
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
+#include <linux/psci.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/types.h>

drivers/soc/qcom/rpmh.c static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr, · line 167

Quoted 9 lines

drivers/soc/qcom/rpmh.c +6 -0

@@ -158,6 +159,13 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
         }
 
  unlock:
+       if (ctrlr->dirty && !psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return ERR_PTR(-EINVAL);
+               }
+       }

It's been a long time since I looked in depth at RPMH, but upon a first glance this seems like it's gonna be terrible for performance. You're going to send every entry again and again, aren't you? In other words in pseudo-code:

1. rpmh_write(addr=0x10, data=0x99);
==> writes on the bus (0x10, 0x99)

2. rpmh_write(addr=0x11, data=0xaa);
==> writes on the bus (0x10, 0x99)
==> writes on the bus (0x11, 0xaa)

3. rpmh_write(addr=0x10, data=0xbb);
==> writes on the bus (0x10, 0xbb)
==> writes on the bus (0x11, 0xaa)

4. rpmh_write(addr=0x12, data=0xcc);
==> writes on the bus (0x10, 0xbb)
==> writes on the bus (0x11, 0xaa)
==> writes on the bus (0x12, 0xcc)

That seems bad.

Why can't you just send the new request itself and forget adding it to the cache? In other words don't even call cache_rpm_request() in the non-OSI case and then in __rpmh_write() just send right away...

I tried to test this and my printouts didn't show anything actually happening in rpmh_flush(). Maybe I just don't have the write patches to exercise this properly...

Quoted 52 lines

drivers/soc/qcom/rpmh.c +13 -4

+
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return req;

@@ -285,26 +293,35 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
  }
  EXPORT_SYMBOL(rpmh_write);
 
-static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
+static int cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
  {
         unsigned long flags;
 
         spin_lock_irqsave(&ctrlr->cache_lock, flags);
+
         list_add_tail(&req->list, &ctrlr->batch_cache);
         ctrlr->dirty = true;
+
+       if (!psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return -EINVAL;
+               }
+       }
+
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+
+       return 0;
  }
 
  static int flush_batch(struct rpmh_ctrlr *ctrlr)
  {
         struct batch_cache_req *req;
         const struct rpmh_request *rpm_msg;
-       unsigned long flags;
         int ret = 0;
         int i;
 
         /* Send Sleep/Wake requests to the controller, expect no response */
-       spin_lock_irqsave(&ctrlr->cache_lock, flags);
         list_for_each_entry(req, &ctrlr->batch_cache, list) {
                 for (i = 0; i < req->count; i++) {
                         rpm_msg = req->rpm_msgs + i;

@@ -314,7 +331,6 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
                                 break;
                 }
         }
-       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return ret;
  }

drivers/soc/qcom/rpmh.c int rpmh_write_batch(const struct device *dev, enum rpmh_state state, · line 406

Quoted 9 lines

drivers/soc/qcom/rpmh.c +2 -4

@@ -386,10 +402,8 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
                 cmd += n[i];
         }
 
-       if (state != RPMH_ACTIVE_ONLY_STATE) {
-               cache_batch(ctrlr, req);
-               return 0;
-       }
+       if (state != RPMH_ACTIVE_ONLY_STATE)
+               return cache_batch(ctrlr, req);

I'm curious: why not just do:

if (state != RPMH_ACTIVE_ONLY_STATE && psci_has_osi_support()) {
   cache_batch(ctrlr, req);
   return 0;
}

...AKA don't even cache it up if we're not in OSI mode. IIUC this would be a huge deal because with your code you're doing the whole RPMH transfer under "spin_lock_irqsave", right? And presumably RPMH transfers are somewhat slow, otherwise why did anyone come up with this whole caching / last-man-down scheme to start with?

OK, it turned out to be at least slightly more complex because it appears that we're supposed to use rpmh_rsc_write_ctrl_data() for sleep/wake stuff and that they never do completions, but it really wasn't too hard. I prototyped it at <http://crrev.com/c/2080916>.
Feel free to hijack that change if it looks like a starting point and if it looks like I'm not too confused.

drivers/soc/qcom/rpmh.c static int send_single(struct rpmh_ctrlr *ctrlr, enum rpmh_state state, · line 460

Quoted 10 lines

drivers/soc/qcom/rpmh.c +0 -3

         for (i = 0; i < count; i++) {
                 struct completion *compl = &compls[i];

@@ -455,9 +469,6 @@ static int send_single(struct rpmh_ctrlr *ctrlr, enum rpmh_state state,
   * Return: -EBUSY if the controller is busy, probably waiting on a response
   * to a RPMH request sent earlier.
   *
- * This function is always called from the sleep code from the last CPU
- * that is powering down the entire system. Since no other RPMH API would be
- * executing at this time, it is safe to run lockless.

Interesting that you removed this comment but not the copy of the comment inside this function. Was that on purpose?

Quoted 72 lines · Doug Anderson

Hi,

Quoted 44 lines · Maulik Shah

Add changes to invoke rpmh flush() from within cache_lock when the data in cache is dirty.

This is done only if OSI is not supported in PSCI. If OSI is supported rpmh_flush can get invoked when the last cpu going to power collapse deepest low power mode.

Also remove "depends on COMPILE_TEST" for Kconfig option QCOM_RPMH so the driver is only compiled for arm64 which supports psci_has_osi_support() API.

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
  drivers/soc/qcom/Kconfig |  2 +-
  drivers/soc/qcom/rpmh.c  | 33 ++++++++++++++++++++++-----------
  2 files changed, 23 insertions(+), 12 deletions(-)

drivers/soc/qcom/Kconfig +1 -1

index d0a73e7..2e581bc 100644
@@ -105,7 +105,7 @@ config QCOM_RMTFS_MEM
 
  config QCOM_RPMH
         bool "Qualcomm RPM-Hardened (RPMH) Communication"
-       depends on ARCH_QCOM && ARM64 || COMPILE_TEST
+       depends on ARCH_QCOM && ARM64
         help
           Support for communication with the hardened-RPM blocks in
           Qualcomm Technologies Inc (QTI) SoCs. RPMH communication uses an

drivers/soc/qcom/rpmh.c +1 -0

index f28afe4..6a5a60c 100644
@@ -12,6 +12,7 @@
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
+#include <linux/psci.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/types.h>

drivers/soc/qcom/rpmh.c static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr, · line 167

Quoted 9 lines

drivers/soc/qcom/rpmh.c +6 -0

@@ -158,6 +159,13 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
         }
 
  unlock:
+       if (ctrlr->dirty && !psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return ERR_PTR(-EINVAL);
+               }
+       }

It's been a long time since I looked in depth at RPMH, but upon a first glance this seems like it's gonna be terrible for performance. You're going to send every entry again and again, aren't you? In other words in pseudo-code:

1. rpmh_write(addr=0x10, data=0x99);
==> writes on the bus (0x10, 0x99)

2. rpmh_write(addr=0x11, data=0xaa);
==> writes on the bus (0x10, 0x99)
==> writes on the bus (0x11, 0xaa)

3. rpmh_write(addr=0x10, data=0xbb);
==> writes on the bus (0x10, 0xbb)
==> writes on the bus (0x11, 0xaa)

Quoted 6 lines

4. rpmh_write(addr=0x12, data=0xcc);
==> writes on the bus (0x10, 0xbb)
==> writes on the bus (0x11, 0xaa)
==> writes on the bus (0x12, 0xcc)

That seems bad.

Hi Doug,

No this is NOT how data is sent to RPMh/AOSS.
The rpmh_flush() fills up DRV-2 (HLOS) TCSes, makes it ready and The HW takes care of
sending data of Sleep TCSes for each of the EL/ DRV(s) when Last cpu is going to deepest
low power mode and of WAKE TCSes while first cpu is waking up.

Quoted 4 lines

Why can't you just send the new request itself and forget adding it to the cache? In other words don't even call cache_rpm_request() in the non-OSI case and then in __rpmh_write() just send right away...

This won’t work out. Let me explain why…

We have 3 SLEEP and 3 WAKE TCSes from below config..

                         qcom,tcs-config = <ACTIVE_TCS  2>,
                                           <SLEEP_TCS   3>,
                                           <WAKE_TCS    3>,

Each TCS has total 16 commands so total 48 commands(16*3) for each SLEEP and WAKE TCSes,
that can be filled up.

Now Lets take a example in pseudo-code on what could happen if we don’t cache and
immediately fill up TCSes commands. The triggering part doesn’t happen as explained above
it fills up TCSes and makes them ready..

Time-t0 (from client_x invoking rpmh_write_batch() for SLEEP SET, a batch of 3 commands)

rpmh_write_batch(
addr=0x10, data=0x99, -> fills up CMD0 in SLEEP TCS_0 addr=0x11, data=0xaa, -> fills up CMD1 in SLEEP TCS_0 addr=0x10, data=0xbb); -> fills up CMD2 in SLEEP TCS_0

Time-t1 (from client_y invoking rpmh_write(), a single command)

rpmh_write(
addr=0x12, data=0xcc, -> fills up CMD3 in SLEEP TCS_0 );

Time-t2 (from client_x invokes rpmh_invalidate() which invalidates all previous *batch requests* only)

At this point, it should have CMD3 only in TCS while CMD 0,1,2 needs to be freed up, since we expect
a new batch request now.

Since driver didn’t cache anything in the first place, it doesn’t know details about previous batch request
like how many commands it had, what were the commands of those batches when filling up in TCSes, and so on…
(basically all the data required to free up only CMD 0,1,2, and don’t disturb CMD3)

Whats more?

The new batch request could be of let say 5 commands after invalidation, instead of 3 commands in previous batch.
So it will not fit in CMD-0,1,2 and we might want to allocate from CMD-4,5,6,7,8 now.

This will leave a hole in TCS CMDs (each TCS has 16 total commands) unless we re-arrange everything.
Also we may want to fill up batch request first and then single requests, by not caching anything, driver don’t
know which one is batch and which one is single request.

There are other cases like below which also gets impacted if driver don't cache anything...

for example, when we don’t have dedicated ACTIVE TCS ( if we have below config with ACTIVE TCS count 0)

     qcom,tcs-config = <ACTIVE_TCS  0>,
                           <SLEEP_TCS   3>,
                           <WAKE_TCS    3>,

Now to send active data, driver may re-use/ re-purpose few of the sleep or wake TCS, to be used as ACTIVE TCS and once work is done, it will be re-allocated in SLEEP/ WAKE TCS pool accordingly. If driver don’t cache, all the SLEEP and WAKE data is lost when one
of TCS is repurposed to use as ACTIVE TCS.

Hope above explanation clears why caching is important and gives clear view of caching v/s not caching.

Thanks,
Maulik

Quoted 3 lines

I tried to test this and my printouts didn't show anything actually happening in rpmh_flush(). Maybe I just don't have the write patches to exercise this properly...

it may be due to missing interconnect patches series
https://patchwork.kernel.org/project/linux-arm-msm/list/?series=247175

Quoted 73 lines

Quoted 51 lines

drivers/soc/qcom/rpmh.c +12 -4

         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return req;

@@ -285,26 +293,35 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
  }
  EXPORT_SYMBOL(rpmh_write);
 
-static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
+static int cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
  {
         unsigned long flags;
 
         spin_lock_irqsave(&ctrlr->cache_lock, flags);
+
         list_add_tail(&req->list, &ctrlr->batch_cache);
         ctrlr->dirty = true;
+
+       if (!psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return -EINVAL;
+               }
+       }
+
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+
+       return 0;
  }
 
  static int flush_batch(struct rpmh_ctrlr *ctrlr)
  {
         struct batch_cache_req *req;
         const struct rpmh_request *rpm_msg;
-       unsigned long flags;
         int ret = 0;
         int i;
 
         /* Send Sleep/Wake requests to the controller, expect no response */
-       spin_lock_irqsave(&ctrlr->cache_lock, flags);
         list_for_each_entry(req, &ctrlr->batch_cache, list) {
                 for (i = 0; i < req->count; i++) {
                         rpm_msg = req->rpm_msgs + i;

@@ -314,7 +331,6 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
                                 break;
                 }
         }
-       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return ret;
  }

drivers/soc/qcom/rpmh.c int rpmh_write_batch(const struct device *dev, enum rpmh_state state, · line 406

Quoted 9 lines

drivers/soc/qcom/rpmh.c +2 -4

@@ -386,10 +402,8 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
                 cmd += n[i];
         }
 
-       if (state != RPMH_ACTIVE_ONLY_STATE) {
-               cache_batch(ctrlr, req);
-               return 0;
-       }
+       if (state != RPMH_ACTIVE_ONLY_STATE)
+               return cache_batch(ctrlr, req);

I'm curious: why not just do:

if (state != RPMH_ACTIVE_ONLY_STATE && psci_has_osi_support()) {
   cache_batch(ctrlr, req);
   return 0;
}

...AKA don't even cache it up if we're not in OSI mode. IIUC this would be a huge deal because with your code you're doing the whole RPMH transfer under "spin_lock_irqsave", right? And presumably RPMH transfers are somewhat slow, otherwise why did anyone come up with this whole caching / last-man-down scheme to start with?

Quoted 6 lines

OK, it turned out to be at least slightly more complex because it appears that we're supposed to use rpmh_rsc_write_ctrl_data() for sleep/wake stuff and that they never do completions, but it really wasn't too hard. I prototyped it at <http://crrev.com/c/2080916>.
Feel free to hijack that change if it looks like a starting point and if it looks like I'm not too confused.

I looked at this change and thought of it earlier but it won’t work out for the reasons in above example.
I have thought of few optimizations in rpmh_flush() to reduce its time, if we *really* see any performance impact…

below is high level idea…
When rpmh_write_batch() is invoked for SLEEP_SETs, currently rpmh_flush() will update both SLEEP and WAKE TCS contents, However we may change it to update only SLEEP TCS, and when rpmh_write_batch() is invoked for WAKE SETs, update only WAKE TCS contents. This way it may reduce time by roughly ~50%.

Hi,

Quoted 80 lines · Maulik Shah

Quoted 72 lines · Doug Anderson

Hi,

Quoted 44 lines · Maulik Shah

Add changes to invoke rpmh flush() from within cache_lock when the data in cache is dirty.

This is done only if OSI is not supported in PSCI. If OSI is supported rpmh_flush can get invoked when the last cpu going to power collapse deepest low power mode.

Also remove "depends on COMPILE_TEST" for Kconfig option QCOM_RPMH so the driver is only compiled for arm64 which supports psci_has_osi_support() API.

Signed-off-by Maulik Shah <[email protected]>

Reviewed-by Srinivas Rao L <[email protected]>

---
  drivers/soc/qcom/Kconfig |  2 +-
  drivers/soc/qcom/rpmh.c  | 33 ++++++++++++++++++++++-----------
  2 files changed, 23 insertions(+), 12 deletions(-)

drivers/soc/qcom/Kconfig +1 -1

index d0a73e7..2e581bc 100644
@@ -105,7 +105,7 @@ config QCOM_RMTFS_MEM
 
  config QCOM_RPMH
         bool "Qualcomm RPM-Hardened (RPMH) Communication"
-       depends on ARCH_QCOM && ARM64 || COMPILE_TEST
+       depends on ARCH_QCOM && ARM64
         help
           Support for communication with the hardened-RPM blocks in
           Qualcomm Technologies Inc (QTI) SoCs. RPMH communication uses an

drivers/soc/qcom/rpmh.c +1 -0

index f28afe4..6a5a60c 100644
@@ -12,6 +12,7 @@
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/platform_device.h>
+#include <linux/psci.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/types.h>

drivers/soc/qcom/rpmh.c static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr, · line 167

Quoted 9 lines

drivers/soc/qcom/rpmh.c +6 -0

@@ -158,6 +159,13 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
         }
 
  unlock:
+       if (ctrlr->dirty && !psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return ERR_PTR(-EINVAL);
+               }
+       }

It's been a long time since I looked in depth at RPMH, but upon a first glance this seems like it's gonna be terrible for performance. You're going to send every entry again and again, aren't you? In other words in pseudo-code:

1. rpmh_write(addr=0x10, data=0x99);
==> writes on the bus (0x10, 0x99)

2. rpmh_write(addr=0x11, data=0xaa);
==> writes on the bus (0x10, 0x99)
==> writes on the bus (0x11, 0xaa)

3. rpmh_write(addr=0x10, data=0xbb);
==> writes on the bus (0x10, 0xbb)
==> writes on the bus (0x11, 0xaa)

Quoted 6 lines

4. rpmh_write(addr=0x12, data=0xcc);
==> writes on the bus (0x10, 0xbb)
==> writes on the bus (0x11, 0xaa)
==> writes on the bus (0x12, 0xcc)

That seems bad.

Quoted 8 lines

Hi Doug,

No this is NOT how data is sent to RPMh/AOSS.
The rpmh_flush() fills up DRV-2 (HLOS) TCSes, makes it ready and The HW takes care of
sending data of Sleep TCSes for each of the EL/ DRV(s) when Last cpu is going to deepest
low power mode and of WAKE TCSes while first cpu is waking up.

Ah, I see. So for sleep / wake commands we never directly wait for them to go out on the bus while the system is awake. We just program them all to the RPMH hardware and they'll set there and all get sent automatically when the last CPU goes into deepest low power mode.

...so actually the whole point of OSI mode (from an RPMH perspective) is not to avoid transactions on the bus. It's just avoiding programming RPMH over and over again. Is that correct?

...and the reason we have all these data structures in the kernel is to keep track of auxiliary information about the things in the sleep/wake TCSs and make it easier to update bits of them?

Quoted 57 lines

Quoted 6 lines

Why can't you just send the new request itself and forget adding it to the cache? In other words don't even call cache_rpm_request() in the non-OSI case and then in __rpmh_write() just send right away...

This won’t work out. Let me explain why…

We have 3 SLEEP and 3 WAKE TCSes from below config..

                         qcom,tcs-config = <ACTIVE_TCS  2>,
                                           <SLEEP_TCS   3>,
                                           <WAKE_TCS    3>,

Each TCS has total 16 commands so total 48 commands(16*3) for each SLEEP and WAKE TCSes,
that can be filled up.

Now Lets take a example in pseudo-code on what could happen if we don’t cache and
immediately fill up TCSes commands. The triggering part doesn’t happen as explained above
it fills up TCSes and makes them ready..

Time-t0 (from client_x invoking rpmh_write_batch() for SLEEP SET, a batch of 3 commands)

rpmh_write_batch(
addr=0x10, data=0x99, -> fills up CMD0 in SLEEP TCS_0 addr=0x11, data=0xaa, -> fills up CMD1 in SLEEP TCS_0 addr=0x10, data=0xbb); -> fills up CMD2 in SLEEP TCS_0

Time-t1 (from client_y invoking rpmh_write(), a single command)

rpmh_write(
addr=0x12, data=0xcc, -> fills up CMD3 in SLEEP TCS_0 );

Time-t2 (from client_x invokes rpmh_invalidate() which invalidates all previous *batch requests* only)

At this point, it should have CMD3 only in TCS while CMD 0,1,2 needs to be freed up, since we expect
a new batch request now.

Since driver didn’t cache anything in the first place, it doesn’t know details about previous batch request
like how many commands it had, what were the commands of those batches when filling up in TCSes, and so on…
(basically all the data required to free up only CMD 0,1,2, and don’t disturb CMD3)

Whats more?

The new batch request could be of let say 5 commands after invalidation, instead of 3 commands in previous batch.
So it will not fit in CMD-0,1,2 and we might want to allocate from CMD-4,5,6,7,8 now.

Quoted 5 lines

This will leave a hole in TCS CMDs (each TCS has 16 total commands) unless we re-arrange everything.
Also we may want to fill up batch request first and then single requests, by not caching anything, driver don’t
know which one is batch and which one is single request.

OK, I got it now. I'll try to spend some time tomorrow looking over everything / testing with my new understanding.

Quoted 9 lines

There are other cases like below which also gets impacted if driver don't cache anything...

for example, when we don’t have dedicated ACTIVE TCS ( if we have below config with ACTIVE TCS count 0)

     qcom,tcs-config = <ACTIVE_TCS  0>,
                           <SLEEP_TCS   3>,
                           <WAKE_TCS    3>,

Quoted 5 lines

Now to send active data, driver may re-use/ re-purpose few of the sleep or wake TCS, to be used as ACTIVE TCS and once work is done, it will be re-allocated in SLEEP/ WAKE TCS pool accordingly. If driver don’t cache, all the SLEEP and WAKE data is lost when one
of TCS is repurposed to use as ACTIVE TCS.

Ah, interesting. I'll read the code more, but are you expecting this type of situation to work today, or is it theoretical for the future?

Quoted 5 lines

Hope above explanation clears why caching is important and gives clear view of caching v/s not caching.

Quoted 8 lines

Thanks,
Maulik

Quoted 3 lines

I tried to test this and my printouts didn't show anything actually happening in rpmh_flush(). Maybe I just don't have the write patches to exercise this properly...

it may be due to missing interconnect patches series
https://patchwork.kernel.org/project/linux-arm-msm/list/?series=247175

I ended up pulling those in but I was still not seeing things work as I expected. I'll debug more tomorrow to see if it was my expectations that were wrong or if there was a real issue.

Quoted 84 lines

Quoted 73 lines

Quoted 51 lines

drivers/soc/qcom/rpmh.c +12 -4

         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return req;

@@ -285,26 +293,35 @@ int rpmh_write(const struct device *dev, enum rpmh_state state,
  }
  EXPORT_SYMBOL(rpmh_write);
 
-static void cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
+static int cache_batch(struct rpmh_ctrlr *ctrlr, struct batch_cache_req *req)
  {
         unsigned long flags;
 
         spin_lock_irqsave(&ctrlr->cache_lock, flags);
+
         list_add_tail(&req->list, &ctrlr->batch_cache);
         ctrlr->dirty = true;
+
+       if (!psci_has_osi_support()) {
+               if (rpmh_flush(ctrlr)) {
+                       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+                       return -EINVAL;
+               }
+       }
+
         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
+
+       return 0;
  }
 
  static int flush_batch(struct rpmh_ctrlr *ctrlr)
  {
         struct batch_cache_req *req;
         const struct rpmh_request *rpm_msg;
-       unsigned long flags;
         int ret = 0;
         int i;
 
         /* Send Sleep/Wake requests to the controller, expect no response */
-       spin_lock_irqsave(&ctrlr->cache_lock, flags);
         list_for_each_entry(req, &ctrlr->batch_cache, list) {
                 for (i = 0; i < req->count; i++) {
                         rpm_msg = req->rpm_msgs + i;

@@ -314,7 +331,6 @@ static int flush_batch(struct rpmh_ctrlr *ctrlr)
                                 break;
                 }
         }
-       spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
 
         return ret;
  }

drivers/soc/qcom/rpmh.c int rpmh_write_batch(const struct device *dev, enum rpmh_state state, · line 406

Quoted 9 lines

drivers/soc/qcom/rpmh.c +2 -4

@@ -386,10 +402,8 @@ int rpmh_write_batch(const struct device *dev, enum rpmh_state state,
                 cmd += n[i];
         }
 
-       if (state != RPMH_ACTIVE_ONLY_STATE) {
-               cache_batch(ctrlr, req);
-               return 0;
-       }
+       if (state != RPMH_ACTIVE_ONLY_STATE)
+               return cache_batch(ctrlr, req);

I'm curious: why not just do:

if (state != RPMH_ACTIVE_ONLY_STATE && psci_has_osi_support()) {
   cache_batch(ctrlr, req);
   return 0;
}

...AKA don't even cache it up if we're not in OSI mode. IIUC this would be a huge deal because with your code you're doing the whole RPMH transfer under "spin_lock_irqsave", right? And presumably RPMH transfers are somewhat slow, otherwise why did anyone come up with this whole caching / last-man-down scheme to start with?

Quoted 6 lines

OK, it turned out to be at least slightly more complex because it appears that we're supposed to use rpmh_rsc_write_ctrl_data() for sleep/wake stuff and that they never do completions, but it really wasn't too hard. I prototyped it at <http://crrev.com/c/2080916>.
Feel free to hijack that change if it looks like a starting point and if it looks like I'm not too confused.

I looked at this change and thought of it earlier but it won’t work out for the reasons in above example.
I have thought of few optimizations in rpmh_flush() to reduce its time, if we *really* see any performance impact…

Quoted 6 lines

below is high level idea…
When rpmh_write_batch() is invoked for SLEEP_SETs, currently rpmh_flush() will update both SLEEP and WAKE TCS contents, However we may change it to update only SLEEP TCS, and when rpmh_write_batch() is invoked for WAKE SETs, update only WAKE TCS contents. This way it may reduce time by roughly ~50%.

OK, that's something to keep in mind. Agree that it doesn't have the be part of the initial change.

-Doug

Quoted 9 lines

There are other cases like below which also gets impacted if driver

Quoted 8 lines

don't cache anything...

for example, when we don’t have dedicated ACTIVE TCS ( if we have below config with ACTIVE TCS count 0)

     qcom,tcs-config = <ACTIVE_TCS  0>,
                           <SLEEP_TCS   3>,
                           <WAKE_TCS    3>,

Quoted 7 lines

Quoted 5 lines

Now to send active data, driver may re-use/ re-purpose few of the sleep or wake TCS, to be used as ACTIVE TCS and once work is done, it will be re-allocated in SLEEP/ WAKE TCS pool accordingly. If driver don’t cache, all the SLEEP and WAKE data is lost when one
of TCS is repurposed to use as ACTIVE TCS.

Ah, interesting. I'll read the code more, but are you expecting this type of situation to work today, or is it theoretical for the future?

yes, we have targets which needs to work with this type of situation.

Hi,

Quoted 9 lines · Maulik Shah

Quoted 9 lines

There are other cases like below which also gets impacted if driver

Quoted 8 lines

don't cache anything...

for example, when we don’t have dedicated ACTIVE TCS ( if we have below config with ACTIVE TCS count 0)

     qcom,tcs-config = <ACTIVE_TCS  0>,
                           <SLEEP_TCS   3>,
                           <WAKE_TCS    3>,

Quoted 8 lines

Quoted 7 lines

Quoted 5 lines

Now to send active data, driver may re-use/ re-purpose few of the sleep or wake TCS, to be used as ACTIVE TCS and once work is done, it will be re-allocated in SLEEP/ WAKE TCS pool accordingly. If driver don’t cache, all the SLEEP and WAKE data is lost when one
of TCS is repurposed to use as ACTIVE TCS.

Ah, interesting. I'll read the code more, but are you expecting this type of situation to work today, or is it theoretical for the future?

yes, we have targets which needs to work with this type of situation.

My brain is still slowly absorbing all the code, but something tells me that targets with no ACTIVE TCS will not work properly with non-OSI mode unless you change your patches more. Specifically to make the zero ACTIVE TCS case work I think you need a rpmh_flush() call after _ALL_ calls to rpmh_write() and rpmh_write_batch() (even those modifying ACTIVE state). rpmh_write_async() will be yet more interesting because you'd have to flush in rpmh_tx_done() I guess? ...and also somehow you need to inhibit entering sleep mode if an async write was in progress? Maybe easier to just detect the "non-OSI-mode + 0 ACTIVE TCS" case at probe time and fail to probe?

-Doug