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

Alex Elder
2022-02-15T22:40:01Z

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?

> + 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.

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