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 > --- > 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 >
