Re: [PATCH v3 19/25] bus: mhi: ep: Add support for handling SYS_ERR condition

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Tue, Feb 15, 2022 at 04:39:55PM -0600, Alex Elder wrote:
> On 2/12/22 12:21 PM, Manivannan Sadhasivam wrote:
> > Add support for handling SYS_ERR (System Error) condition in the MHI
> > endpoint stack. The SYS_ERR flag will be asserted by the endpoint device
> > when it detects an internal error. The host will then issue reset and
> > reinitializes MHI to recover from the error state.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> 
> I have a few small comments, but this look good enough for me.
> 
> Reviewed-by: Alex Elder <elder@linaro.org>
> 
> > ---
> >   drivers/bus/mhi/ep/internal.h |  1 +
> >   drivers/bus/mhi/ep/main.c     | 24 ++++++++++++++++++++++++
> >   drivers/bus/mhi/ep/sm.c       |  2 ++
> >   3 files changed, 27 insertions(+)
> > 
> > diff --git a/drivers/bus/mhi/ep/internal.h b/drivers/bus/mhi/ep/internal.h
> > index ee8c5974f0c0..8654af7caf40 100644
> > --- a/drivers/bus/mhi/ep/internal.h
> > +++ b/drivers/bus/mhi/ep/internal.h
> > @@ -241,6 +241,7 @@ int mhi_ep_set_mhi_state(struct mhi_ep_cntrl *mhi_cntrl, enum mhi_state mhi_stat
> >   int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl);
> >   int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl);
> >   int mhi_ep_set_ready_state(struct mhi_ep_cntrl *mhi_cntrl);
> > +void mhi_ep_handle_syserr(struct mhi_ep_cntrl *mhi_cntrl);
> >   /* MHI EP memory management functions */
> >   int mhi_ep_alloc_map(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr, size_t size,
> > diff --git a/drivers/bus/mhi/ep/main.c b/drivers/bus/mhi/ep/main.c
> > index ddedd0fb19aa..6378ac5c7e37 100644
> > --- a/drivers/bus/mhi/ep/main.c
> > +++ b/drivers/bus/mhi/ep/main.c
> > @@ -611,6 +611,30 @@ static void mhi_ep_reset_worker(struct work_struct *work)
> >   	}
> >   }
> > +/*
> > + * We don't need to do anything special other than setting the MHI SYS_ERR
> > + * state. The host issue will reset all contexts and issue MHI RESET so that we
> 
> s/host issue/host/
> 
> > + * could also recover from error state.
> > + */
> > +void mhi_ep_handle_syserr(struct mhi_ep_cntrl *mhi_cntrl)
> > +{
> > +	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > +	int ret;
> > +
> > +	/* If MHI EP is not enabled, nothing to do */
> > +	if (!mhi_cntrl->is_enabled)
> 
> Is this an expected condition?  SYS_ERR with the endpoint
> disabled?
> 

I hit a case during bringup but I don't exactly remember where. So I'll probably
remove this check.

> > +		return;
> > +
> > +	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_SYS_ERR);
> > +	if (ret)
> > +		return;
> > +
> > +	/* Signal host that the device went to SYS_ERR state */
> > +	ret = mhi_ep_send_state_change_event(mhi_cntrl, MHI_STATE_SYS_ERR);
> > +	if (ret)
> > +		dev_err(dev, "Failed sending SYS_ERR state change event: %d\n", ret);
> > +}
> > +
> >   int mhi_ep_power_up(struct mhi_ep_cntrl *mhi_cntrl)
> >   {
> >   	struct device *dev = &mhi_cntrl->mhi_dev->dev;
> > diff --git a/drivers/bus/mhi/ep/sm.c b/drivers/bus/mhi/ep/sm.c
> > index 68e7f99b9137..9a75ecfe1adf 100644
> > --- a/drivers/bus/mhi/ep/sm.c
> > +++ b/drivers/bus/mhi/ep/sm.c
> > @@ -93,6 +93,7 @@ int mhi_ep_set_m0_state(struct mhi_ep_cntrl *mhi_cntrl)
> >   	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M0);
> >   	if (ret) {
> > +		mhi_ep_handle_syserr(mhi_cntrl);
> >   		spin_unlock_bh(&mhi_cntrl->state_lock);
> >   		return ret;
> >   	}
> > @@ -128,6 +129,7 @@ int mhi_ep_set_m3_state(struct mhi_ep_cntrl *mhi_cntrl)
> >   	spin_lock_bh(&mhi_cntrl->state_lock);
> >   	ret = mhi_ep_set_mhi_state(mhi_cntrl, MHI_STATE_M3);
> 
> Are there any other spots that should do this?  For example, in
> mhi_ep_set_ready_state() you don't check the return value of
> the call to mhi_ep_set_mhi_state().  It seems to me it should
> be possible to preclude bogus state changes anyway, but I'm
> not completely sure.
> 

The check should be there, I will add it to ready_state() also.

Thanks,
Mani

> >   	if (ret) {
> > +		mhi_ep_handle_syserr(mhi_cntrl);
> >   		spin_unlock_bh(&mhi_cntrl->state_lock);
> >   		return ret;
> >   	}
>