bus: mhi: Wait for M2 state during system resume

During system resume, MHI host triggers M3->M0 transition and then waits for target device to enter M0 state. Once done, the device queues a state change event into ctrl event ring and notifies MHI host by raising an interrupt, where a tasklet is scheduled to process this event. In most cases, the tasklet is served timely and wait operation succeeds.

However, there are cases where CPU is busy and cannot serve this tasklet for some time. Once delay goes long enough, the device moves itself to M1 state and also interrupts MHI host after inserting a new state change event to ctrl ring. Later CPU finally has time to process the ring, however there are two events in it now:
1. for M3->M0 event, which is processed first as queued first, tasklet handler updates device state to M0 and wakes up the task, i.e., the MHI host.
2. for M0->M1 event, which is processed later, tasklet handler triggers M1->M2 transition and updates device state to M2 directly, then wakes up the MHI host(if still sleeping on this wait queue).
Note that although MHI host has been woken up while processing the first event, it may still has no chance to run before the second event is processed. In other words, MHI host has to keep waiting till timeout cause the M0 state has been missed.

kernel log here:
...

Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.911251] mhi 0000:06:00.0: Entered with PM state: M3, MHI state: M3
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917762] mhi 0000:06:00.0: State change event to state: M0
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917767] mhi 0000:06:00.0: State change event to state: M1
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4338.788231] mhi 0000:06:00.0: Did not enter M0 state, MHI state: M2, PM state: M2

...

Fix this issue by simply adding M2 as a valid state for resume.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Fixes 0c6b20a1d720 ("bus: mhi: core: Add support for MHI suspend and resume")

Signed-off-by Baochen Qiang <[email protected]>

Reviewed-by Hemant Kumar <[email protected]>

---
 drivers/bus/mhi/core/pm.c | 1 +
 1 file changed, 1 insertion(+)

drivers/bus/mhi/core/pm.c +1 -0

index e2e59a341fef..59b009a3ee9b 100644
@@ -934,6 +934,7 @@ int mhi_pm_resume(struct mhi_controller *mhi_cntrl)
 
 	ret = wait_event_timeout(mhi_cntrl->state_event,
 				 mhi_cntrl->dev_state == MHI_STATE_M0 ||
+				 mhi_cntrl->dev_state == MHI_STATE_M2 ||
 				 MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state),
 				 msecs_to_jiffies(mhi_cntrl->timeout_ms));
 

Signature · 1 line

2.25.1

During system resume, MHI host triggers M3->M0 transition and then waits for target device to enter M0 state. Once done, the device queues a state change event into ctrl event ring and notifies MHI host by raising an interrupt, where a tasklet is scheduled to process this event. In most cases, the tasklet is served timely and wait operation succeeds.

However, there are cases where CPU is busy and cannot serve this tasklet for some time. Once delay goes long enough, the device moves itself to M1 state and also interrupts MHI host after inserting a new state change event to ctrl ring. Later CPU finally has time to process the ring, however there are two events in it now:
1. for M3->M0 event, which is processed first as queued first, tasklet handler updates device state to M0 and wakes up the task, i.e., the MHI host.
2. for M0->M1 event, which is processed later, tasklet handler triggers M1->M2 transition and updates device state to M2 directly, then wakes up the MHI host(if still sleeping on this wait queue).
Note that although MHI host has been woken up while processing the first event, it may still has no chance to run before the second event is processed. In other words, MHI host has to keep waiting till timeout cause the M0 state has been missed.

kernel log here:
...

Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.911251] mhi 0000:06:00.0: Entered with PM state: M3, MHI state: M3
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917762] mhi 0000:06:00.0: State change event to state: M0
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917767] mhi 0000:06:00.0: State change event to state: M1
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4338.788231] mhi 0000:06:00.0: Did not enter M0 state, MHI state: M2, PM state: M2

...

Fix this issue by simply adding M2 as a valid state for resume.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Fixes 0c6b20a1d720 ("bus: mhi: core: Add support for MHI suspend and resume")

Signed-off-by Baochen Qiang <[email protected]>

Reviewed-by Hemant Kumar <[email protected]>

---
 drivers/bus/mhi/core/pm.c | 1 +
 1 file changed, 1 insertion(+)

drivers/bus/mhi/core/pm.c +1 -0

index e2e59a341fef..59b009a3ee9b 100644
@@ -934,6 +934,7 @@ int mhi_pm_resume(struct mhi_controller *mhi_cntrl)
 
 	ret = wait_event_timeout(mhi_cntrl->state_event,
 				 mhi_cntrl->dev_state == MHI_STATE_M0 ||
+				 mhi_cntrl->dev_state == MHI_STATE_M2 ||
 				 MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state),
 				 msecs_to_jiffies(mhi_cntrl->timeout_ms));
 

Signature · 1 line

2.25.1

Quoted 32 lines · Baochen Qiang

During system resume, MHI host triggers M3->M0 transition and then waits for target device to enter M0 state. Once done, the device queues a state change event into ctrl event ring and notifies MHI host by raising an interrupt, where a tasklet is scheduled to process this event. In most cases, the tasklet is served timely and wait operation succeeds.

However, there are cases where CPU is busy and cannot serve this tasklet for some time. Once delay goes long enough, the device moves itself to M1 state and also interrupts MHI host after inserting a new state change event to ctrl ring. Later CPU finally has time to process the ring, however there are two events in it now:
1. for M3->M0 event, which is processed first as queued first, tasklet handler updates device state to M0 and wakes up the task, i.e., the MHI host.
2. for M0->M1 event, which is processed later, tasklet handler triggers M1->M2 transition and updates device state to M2 directly, then wakes up the MHI host(if still sleeping on this wait queue).
Note that although MHI host has been woken up while processing the first event, it may still has no chance to run before the second event is processed. In other words, MHI host has to keep waiting till timeout cause the M0 state has been missed.

kernel log here:
...

Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.911251] mhi 0000:06:00.0: Entered with PM state: M3, MHI state: M3
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917762] mhi 0000:06:00.0: State change event to state: M0
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917767] mhi 0000:06:00.0: State change event to state: M1
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4338.788231] mhi 0000:06:00.0: Did not enter M0 state, MHI state: M2, PM state: M2

...

Fix this issue by simply adding M2 as a valid state for resume.

Quoted 5 lines

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Fixes 0c6b20a1d720 ("bus: mhi: core: Add support for MHI suspend and resume")

Signed-off-by Baochen Qiang <[email protected]>

Reviewed-by Hemant Kumar <[email protected]>

Applied to mhi-fixes!

Thanks,
Mani

Quoted 19 lines

---
 drivers/bus/mhi/core/pm.c | 1 +
 1 file changed, 1 insertion(+)

drivers/bus/mhi/core/pm.c +1 -0

index e2e59a341fef..59b009a3ee9b 100644
@@ -934,6 +934,7 @@ int mhi_pm_resume(struct mhi_controller *mhi_cntrl)
 
 	ret = wait_event_timeout(mhi_cntrl->state_event,
 				 mhi_cntrl->dev_state == MHI_STATE_M0 ||
+				 mhi_cntrl->dev_state == MHI_STATE_M2 ||
 				 MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state),
 				 msecs_to_jiffies(mhi_cntrl->timeout_ms));
 

Signature · 1 line

2.25.1

During system resume, MHI host triggers M3->M0 transition and then waits for target device to enter M0 state. Once done, the device queues a state change event into ctrl event ring and notifies MHI host by raising an interrupt, where a tasklet is scheduled to process this event. In most cases, the tasklet is served timely and wait operation succeeds.

However, there are cases where CPU is busy and cannot serve this tasklet for some time. Once delay goes long enough, the device moves itself to M1 state and also interrupts MHI host after inserting a new state change event to ctrl ring. Later CPU finally has time to process the ring, however there are two events in it now:
1. for M3->M0 event, which is processed first as queued first, tasklet handler updates device state to M0 and wakes up the task, i.e., the MHI host.
2. for M0->M1 event, which is processed later, tasklet handler triggers M1->M2 transition and updates device state to M2 directly, then wakes up the MHI host(if still sleeping on this wait queue).
Note that although MHI host has been woken up while processing the first event, it may still has no chance to run before the second event is processed. In other words, MHI host has to keep waiting till timeout cause the M0 state has been missed.

kernel log here:
...

Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.911251] mhi 0000:06:00.0: Entered with PM state: M3, MHI state: M3
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917762] mhi 0000:06:00.0: State change event to state: M0
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917767] mhi 0000:06:00.0: State change event to state: M1
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4338.788231] mhi 0000:06:00.0: Did not enter M0 state, MHI state: M2, PM state: M2

...

Fix this issue by simply adding M2 as a valid state for resume.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Fixes 0c6b20a1d720 ("bus: mhi: core: Add support for MHI suspend and resume")

Signed-off-by Baochen Qiang <[email protected]>

Reviewed-by Hemant Kumar <[email protected]>

---
 drivers/bus/mhi/core/pm.c | 1 +
 1 file changed, 1 insertion(+)

Quoted 32 lines · Baochen Qiang

During system resume, MHI host triggers M3->M0 transition and then waits for target device to enter M0 state. Once done, the device queues a state change event into ctrl event ring and notifies MHI host by raising an interrupt, where a tasklet is scheduled to process this event. In most cases, the tasklet is served timely and wait operation succeeds.

However, there are cases where CPU is busy and cannot serve this tasklet for some time. Once delay goes long enough, the device moves itself to M1 state and also interrupts MHI host after inserting a new state change event to ctrl ring. Later CPU finally has time to process the ring, however there are two events in it now:
1. for M3->M0 event, which is processed first as queued first, tasklet handler updates device state to M0 and wakes up the task, i.e., the MHI host.
2. for M0->M1 event, which is processed later, tasklet handler triggers M1->M2 transition and updates device state to M2 directly, then wakes up the MHI host(if still sleeping on this wait queue).
Note that although MHI host has been woken up while processing the first event, it may still has no chance to run before the second event is processed. In other words, MHI host has to keep waiting till timeout cause the M0 state has been missed.

kernel log here:
...

Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.911251] mhi 0000:06:00.0: Entered with PM state: M3, MHI state: M3
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917762] mhi 0000:06:00.0: State change event to state: M0
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4247.917767] mhi 0000:06:00.0: State change event to state: M1
Apr 15 01:45:14 test-NUC8i7HVK kernel: [ 4338.788231] mhi 0000:06:00.0: Did not enter M0 state, MHI state: M2, PM state: M2

...

Fix this issue by simply adding M2 as a valid state for resume.

Quoted 8 lines

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

Fixes 0c6b20a1d720 ("bus: mhi: core: Add support for MHI suspend and resume")

Signed-off-by Baochen Qiang <[email protected]>

Reviewed-by Hemant Kumar <[email protected]>

---
 drivers/bus/mhi/core/pm.c | 1 +
 1 file changed, 1 insertion(+)

<formletter>

This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>