linux-kernel - Re: [PATCH v5 6/9] bus: mhi: core: Check channel execution environment before issuing reset

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Message-ID: <20210121151226.GD5473@work>
Date:   Thu, 21 Jan 2021 20:42:26 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bhaumik Bhatt <bbhatt@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, hemantk@...eaurora.org,
        jhugo@...eaurora.org, linux-kernel@...r.kernel.org,
        loic.poulain@...aro.org
Subject: Re: [PATCH v5 6/9] bus: mhi: core: Check channel execution
 environment before issuing reset

On Fri, Jan 08, 2021 at 12:54:54PM -0800, Bhaumik Bhatt wrote:
> A client can attempt to unprepare certain channels for transfer even
> after the execution environment they are supposed to run in has changed.

Just out of curiosity, under what circumstances it can happen? We don't
have any in kernel user for the mhi_unprepare_from_transfer() API :/

> In the event that happens, the device need not be notified of the reset
> and the host can proceed with clean up for the channel context and
> memory allocated for it on the host as the device will no longer be able
> to respond to such a request.
> 
> Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
> Reviewed-by: Hemant Kumar <hemantk@...eaurora.org>
> ---
>  drivers/bus/mhi/core/main.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index a84e6aa..ec720fe 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1351,11 +1351,24 @@ static void __mhi_unprepare_channel(struct mhi_controller *mhi_cntrl,
>  	/* no more processing events for this channel */
>  	mutex_lock(&mhi_chan->mutex);
>  
> +	if (!(BIT(mhi_cntrl->ee) & mhi_chan->ee_mask)) {
> +		dev_err(dev,
> +			"Current EE: %s Required EE Mask: 0x%x for chan: %s\n",
> +			TO_MHI_EXEC_STR(mhi_cntrl->ee), mhi_chan->ee_mask,
> +			mhi_chan->name);

Again, use channel's struct dev here.

Thanks,
Mani