mmc: changes to enable runtime PM of mmc core layer
PATCH 3/3 mmc: changes to enable runtime PM of mmc core layer
Quoted 2 lines
From
cac07f43de68615cca9f01f619870fdce05df2a2Mon Sep 17 00:00:00 2001
From: Yunpeng Gao <[email protected]>
Date: Sun, 28 Nov 2010 13:00:42 +0800
Subject: [PATCH] Do some changes in mmc core layer to enable mmc card runtime pm.
Seems current runtime PM support in mmc core layer has some problems:
1. If host controller is PCI device, then it's possibly that the PCI host controller will be runtime suspended immediately after its PCI probe. Then it will have trouble when do the following mmc_rescan since at that time the function driver (mmc block driver or sdio function driver) has not been called and there's no chance to execute pm_runtime_get().
2. Currently mmc_host_class (defined in drivers/mmc/core/host.c) is parent of mmc_card and child of host controller. But mmc_host_class has not implemented the runtime pm APIs of itself. So seems it'll cause the mmc runtime PM chain disconnect here.
This patch tries to fix above 2 problems.
For 1, it adds pm_runtime_get/put at the begging/end of function mmc_rescan().
For2, it implements a set of dummy runtime PM API for the mmc_host_class.
--- drivers/mmc/core/bus.c | 2 +- drivers/mmc/core/core.c | 4 ++++ drivers/mmc/core/host.c | 35 +++++++++++++++++++++++++++++++++++ 3 files changed, 40 insertions(+), 1 deletions(-)
drivers/mmc/core/bus.c +1 -1
@@ -160,7 +160,7 @@ static int mmc_runtime_resume(struct device *dev)static int mmc_runtime_idle (struct device *dev) { -return pm_runtime_suspend (dev); +return pm_schedule_suspend (dev,100 ); }static const struct dev_pm_ops mmc_bus_pm_ops = {
drivers/mmc/core/core.c +4 -0
@@ -22,6 +22,7 @@#include <linux/scatterlist.h> #include <linux/log2.h> #include <linux/regulator/consumer.h> +#include <linux/pm_runtime.h> #include <linux/mmc/card.h> #include <linux/mmc/host.h>
@@ -1503,6 +1504,7 @@ void mmc_rescan(struct work_struct *work)spin_unlock_irqrestore (&host->lock, flags); +pm_runtime_get_sync (host->parent);mmc_bus_get (host);
@@ -1598,6 +1600,8 @@ out_fail:mmc_power_off (host); } out: +pm_runtime_put_sync (host->parent); +if (host->caps &MMC_CAP_NEEDS_POLL )mmc_schedule_delayed_work (&host->detect,HZ ); }
drivers/mmc/core/host.c +35 -0
@@ -19,6 +19,7 @@#include <linux/leds.h> #include <linux/slab.h> #include <linux/suspend.h> +#include <linux/pm_runtime.h> #include <linux/mmc/host.h> #include <linux/mmc/card.h>
@@ -28,6 +29,33 @@#define cls_dev_to_mmc_host (d) container_of(d, struct mmc_host, class_dev) +#ifdef CONFIG_PM_RUNTIME +static int mmc_host_runtime_suspend (struct device *dev) +{ +return 0 ; +} + +static int mmc_host_runtime_resume (struct device *dev) +{ +return 0 ; +} + +static int mmc_host_runtime_idle (struct device *dev) +{ +return pm_runtime_suspend (dev); +} +#else +#define mmc_host_runtime_suspend NULL +#define mmc_host_runtime_resume NULL +#define mmc_host_runtime_idle NULL +#endif + +const static struct dev_pm_ops host_pm = { + .runtime_suspend = mmc_host_runtime_suspend, + .runtime_resume = mmc_host_runtime_resume, + .runtime_idle = mmc_host_runtime_idle, +}; +static void mmc_host_classdev_release (struct device *dev) {struct mmc_host *host =cls_dev_to_mmc_host (dev);
@@ -37,6 +65,7 @@ static void mmc_host_classdev_release(struct device *dev)static struct class mmc_host_class = { .name ="mmc_host" , .dev_release = mmc_host_classdev_release, + .pm = &host_pm, };int mmc_register_host_class (void )
@@ -333,6 +362,12 @@ int mmc_add_host(struct mmc_host *host)if (err)return err; +/* Enable runtime PM */ +pm_runtime_get_noresume (&host->class_dev); +pm_runtime_set_active (&host->class_dev); +pm_runtime_enable (&host->class_dev); +pm_runtime_put_sync (&host->class_dev); +#ifdef CONFIG_DEBUG_FS mmc_add_host_debugfs (host);#endif
Signature · 1 line
1.6.6.1
Hi Yunpeng,
Quoted 4 lines · Yunpeng Gao
static int
mmc_runtime_idle(struct device *dev)
{
- returnpm_runtime_suspend(dev);
+ returnpm_schedule_suspend(dev, 100);
You shouldn't do this here.
You didn't comment about or mentioned this change, but I guess you did it because you (quite reasonably) didn't want the card to be powered off as soon as mmc_blk_issue_rq() completes, and instead, you preferred to wait until some period of inactivity time passes.
But that's not true for all mmc buses: e.g., when an SDIO function driver decides it's time to power off the card (e.g. user disables the wlan interface), there is no reason to have this delay.
In addition, putting an inherent delay here will completely prevent anyone from achieving a synchronous idle notification on an mmc card (so even pm_runtime_put_sync() will now set a timer to submit a suspend request instead of carrying out a synchronous suspend).
It looks like you can drop this change, and instead just use the autosuspend API from the mmc block driver (mainly use pm_runtime_put_autosuspend() instead of pm_runtime_put()).
Another nice benefit of autosuspend is that now user space will be able to tweak the amount of delay by using /sys/devices/.../power/autosuspend_delay_ms attribute.
Quoted 32 lines
drivers/mmc/core/host.c +17
-0@@ -19,6 +19,7 @@ #include <linux/leds.h> #include <linux/slab.h> #include <linux/suspend.h> +#include <linux/pm_runtime.h> #include <linux/mmc/host.h> #include <linux/mmc/card.h>@@ -28,6 +29,33 @@ #define cls_dev_to_mmc_host(d) container_of(d, struct mmc_host, class_dev) +#ifdef CONFIG_PM_RUNTIME +static int mmc_host_runtime_suspend (struct device *dev) +{ + return 0; +} + +static int mmc_host_runtime_resume (struct device *dev) +{ + return 0; +} + +static int mmc_host_runtime_idle (struct device *dev) +{ + return pm_runtime_suspend(dev); +} +#else
drivers/mmc/core/host.c line 57
Quoted 10 lines
drivers/mmc/core/host.c +10
-0+#define mmc_host_runtime_suspend NULL +#define mmc_host_runtime_resume NULL +#define mmc_host_runtime_idle NULL +#endif + +const static struct dev_pm_ops host_pm = { + .runtime_suspend = mmc_host_runtime_suspend, + .runtime_resume = mmc_host_runtime_resume, + .runtime_idle = mmc_host_runtime_idle, +};
Since the host's classdev is just a logical sub device of the parent, and will never be power managed on its own, we don't really need those handlers.
Instead, you can just call pm_runtime_no_callbacks(). This will tell the PM core to assume that ->runtime_idle() always invokes ->runtime_suspend(), and that the ->runtime_{suspend, resume} callbacks always succeed.
Quoted 13 lines
drivers/mmc/core/host.c +2
-0+ static void mmc_host_classdev_release(struct device *dev) { struct mmc_host *host = cls_dev_to_mmc_host(dev);@@ -37,6 +65,7 @@ static void mmc_host_classdev_release(struct device *dev) static struct class mmc_host_class = { .name = "mmc_host", .dev_release = mmc_host_classdev_release, + .pm = &host_pm, }; int mmc_register_host_class(void)
drivers/mmc/core/host.c int mmc_add_host(struct mmc_host *host) · line 369
Quoted 8 lines
drivers/mmc/core/host.c +5
-0@@ -333,6 +362,12 @@ int mmc_add_host(struct mmc_host *host) if (err) return err; + /* Enable runtime PM */ + pm_runtime_get_noresume(&host->class_dev); + pm_runtime_set_active(&host->class_dev); + pm_runtime_enable(&host->class_dev); + pm_runtime_put_sync(&host->class_dev);
Why do you need the get_noresume() and put_sync() calls here ?
If you put it in order to ensure the device is automatically powered off after enabling runtime pm, you can just move the set_active() and enable() calls a few lines upwards that function, just _before_ you add the device to the device tree.
Thanks,
Ohad.
Quoted 12 lines
drivers/mmc/core/host.c +1
-1+ #ifdef CONFIG_DEBUG_FS mmc_add_host_debugfs(host); #endif --1.6.6.1
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Quoted 16 lines
You shouldn't do this here.
You didn't comment about or mentioned this change, but I guess you did it because you (quite reasonably) didn't want the card to be powered off as soon as
mmc_blk_issue_rq()completes, and instead, you preferred to wait until some period of inactivity time passes.But that's not true for all mmc buses: e.g., when an SDIO function driver decides it's time to power off the card (e.g. user disables the wlan interface), there is no reason to have this delay.
In addition, putting an inherent delay here will completely prevent anyone from achieving a synchronous idle notification on an mmc card (so even
pm_runtime_put_sync()will now set a timer to submit a suspend request instead of carrying out a synchronous suspend).
Quoted 7 lines
It looks like you can drop this change, and instead just use the autosuspend API from the mmc block driver (mainly use
pm_runtime_put_autosuspend()instead ofpm_runtime_put()).Another nice benefit of autosuspend is that now user space will be able to tweak the amount of delay by using
/sys/devices/.../power/autosuspend_delay_msattribute.
Thanks a lot for the nice review and comments. They're very valuable to me. I'll read it carefully and resubmit these patches later. Thank you again :-)