Re: [PATCH v2] mhi: Fix invalid error returning in mhi_queue

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

On Fri, Feb 26, 2021 at 11:53:02AM +0100, Loic Poulain wrote:
> mhi_queue returns an error when the doorbell is not accessible in
> the current state. This can happen when the device is in non M0
> state, like M3, and needs to be waken-up prior ringing the DB. This
> case is managed earlier by triggering an asynchronous M3 exit via
> controller resume/suspend callbacks, that in turn will cause M0
> transition and DB update.
> 
> So, since it's not an error but just delaying of doorbell update, there
> is no reason to return an error.
> 
> This also fixes a use after free error for skb case, indeed a caller
> queuing skb will try to free the skb if the queueing fails, but in
> that case queueing has been done.
> 
> Fixes: a8f75cb348fd ("mhi: core: Factorize mhi queuing")
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> Reviewed-by: Jeffrey Hugo <jhugo@codeaurora.org>
> Reviewed-by: Bhaumik Bhatt <bbhatt@codeaurora.org>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  v2: - Fix/reword commit message
>      - Add Fixes tag
> 
>  drivers/bus/mhi/core/main.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index 7fc2482..c780234 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -1031,12 +1031,8 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
>  	if (mhi_chan->dir == DMA_TO_DEVICE)
>  		atomic_inc(&mhi_cntrl->pending_pkts);
>  
> -	if (unlikely(!MHI_DB_ACCESS_VALID(mhi_cntrl))) {
> -		ret = -EIO;
> -		goto exit_unlock;
> -	}
> -
> -	mhi_ring_chan_db(mhi_cntrl, mhi_chan);
> +	if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
> +		mhi_ring_chan_db(mhi_cntrl, mhi_chan);
>  
>  exit_unlock:
>  	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
> -- 
> 2.7.4
>