Re: [PATCH v4] bus: mhi: host: Skip MHI reset if device is in RDDM

[Qiang Yu]

On 5/19/2023 9:51 PM, Manivannan Sadhasivam wrote:
> On Thu, May 18, 2023 at 02:22:39PM +0800, Qiang Yu wrote:
> > In RDDM EE, device can not process MHI reset issued by host. In case of MHI
> > power off, host is issuing MHI reset and polls for it to get cleared until
> > it times out. Since this timeout can not be avoided in case of RDDM, skip
> > the MHI reset in this scenarios.
> >
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Fixes: a6e2e3522f29 ("bus: mhi: core: Add support for PM state transitions")
> > Signed-off-by: Qiang Yu <quic_qianyu@xxxxxxxxxxx>
> > Reviewed-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
> > ---
> > v1->v2: use ~75 columns in commit text, add Fixes tag
> > v2->v3: update Fixes tag
> > v3->v4: add review tag and CC stable
> >
> >   drivers/bus/mhi/host/pm.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
> > index 0834590..8a4362d 100644
> > --- a/drivers/bus/mhi/host/pm.c
> > +++ b/drivers/bus/mhi/host/pm.c
> > @@ -470,6 +470,10 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
> >   
> >   	/* Trigger MHI RESET so that the device will not access host memory */
> >   	if (!MHI_PM_IN_FATAL_STATE(mhi_cntrl->pm_state)) {
> > +		/* Skip MHI RESET if in RDDM state */
> > +		if (mhi_cntrl->rddm_image && mhi_get_exec_env(mhi_cntrl) == MHI_EE_RDDM)
> Do we really need to check for rddm_image? Wouldn't the EE check sufficient
> enough?
>
> In that case, the check can be moved to the prior if condition.
>
> - Mani

If rddm_image is NULL, that means this device does not support RDDM. In this case, it is unnecessary to access MMIO register.

> > +			goto skip_mhi_reset;
> > +
> >   		dev_dbg(dev, "Triggering MHI Reset in device\n");
> >   		mhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);
> >   
> > @@ -495,6 +499,7 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
> >   		}
> >   	}
> >   
> > +skip_mhi_reset:
> >   	dev_dbg(dev,
> >   		 "Waiting for all pending event ring processing to complete\n");
> >   	mhi_event = mhi_cntrl->mhi_event;
> > --
> > 2.7.4