Re: [PATCH] mhi: add MHI_STATE_M2 to resume success criteria

[bqiang]

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