linux-kernel - Re: [PATCH v3 19/25] bus: mhi: ep: Add support for handling SYS

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Message-ID: <40212d64-7423-014a-2a8d-cad5cc41795f@linaro.org>
Date:   Tue, 15 Feb 2022 16:39:55 -0600
From:   Alex Elder <elder@...aro.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        mhi@...ts.linux.dev
Cc:     quic_hemantk@...cinc.com, quic_bbhatt@...cinc.com,
        quic_jhugo@...cinc.com, vinod.koul@...aro.org,
        bjorn.andersson@...aro.org, dmitry.baryshkov@...aro.org,
        quic_vbadigan@...cinc.com, quic_cang@...cinc.com,
        quic_skananth@...cinc.com, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 19/25] bus: mhi: ep: Add support for handling SYS_ERR
 condition

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@...aro.org>

I have a few small comments, but this look good enough for me.

Reviewed-by: Alex Elder <elder@...aro.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;
>   	}