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

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Message-ID: <20230519135129.GA4843@thinkpad>
Date:   Fri, 19 May 2023 19:21:29 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Qiang Yu <quic_qianyu@...cinc.com>
Cc:     mani@...nel.org, quic_jhugo@...cinc.com, mhi@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_cang@...cinc.com, quic_mrana@...cinc.com,
        stable@...r.kernel.org
Subject: Re: [PATCH v4] bus: mhi: host: Skip MHI reset if device is in RDDM

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@...r.kernel.org>
> Fixes: a6e2e3522f29 ("bus: mhi: core: Add support for PM state transitions")
> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
> Reviewed-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
> ---
> 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

> +			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
> 
> 

-- 
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