On 2021-05-21 20:45, Manivannan Sadhasivam wrote:
Hi,
The patch subject should be,
"bus: mhi: Wait for M2 state during system resume"
We follow "bus: mhi:" prefix for all MHI patches. Also, the subject
should
clearly portray what the patch is intend to do.
On Tue, Apr 20, 2021 at 11:53:39AM +0800, Baochen Qiang wrote:
During system resume, mhi driver triggers M3->M0 transition and then
waits
s/mhi driver/MHI host
for target device to enter M0 state. Once done, the device queues a
state
change event into ctrl event ring and notify mhi dirver by raising an
s/notify/notifies and s/mhi dirver/MHI host. MHI driver is somewhat
confusing
since we have the MHI device driver (QRTR etc...) as well. So just use
MHI host
everywhere.
interrupt, where a tasklet is scheduled to process this event. In most
cases,
the taklet is served timely and wait operation succeeds.
s/taklet/tasklet
However, there are cases where CPU is busy and can not serve this
tasklet
a/can not/cannot
for some time. Once delay goes long enough, the device moves itself to
M1
state and also interrupts mhi driver 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 driver.
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 driver(if still sleeping on this wait
queue).
Note that although mhi driver 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 driver 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
Signed-off-by: Baochen Qiang <bqiang@xxxxxxxxxxxxxx>
Could you please add a fixes tag as well? And this patch should be
backported to
stable kernels also, so please CC stable@xxxxxxxxxxxxxxx.
Thanks,
Mani
Thanks Mani.
Will address them and send as V2.
---
drivers/bus/mhi/core/pm.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index ce73cfa63cb3..ca5f2feed9d5 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -900,6 +900,7 @@ 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));
--
2.25.1
