Re: [PATCH v2 1/2] bus: mhi: core: Fix MHI runtime_pm behavior

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

On Tue, Apr 06, 2021 at 11:11:54AM +0200, Loic Poulain wrote:
> This change ensures that PM reference is always get during packet
> queueing and released either after queuing completion (RX) or once
> the buffer has been consumed (TX). This guarantees proper update for
> underlying MHI controller runtime status (e.g. last_busy timestamp)
> and prevents suspend to be triggered while TX packets are flying,
> or before we completed update of the RX ring.
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>

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

Thanks,
Mani

> ---
>  v2: mhi_reset_data_chan: move put under existing DMA_TO_DEVICE if block
> 
>  drivers/bus/mhi/core/main.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index c780234..6e72239 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -584,8 +584,11 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
>  			/* notify client */
>  			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
>  
> -			if (mhi_chan->dir == DMA_TO_DEVICE)
> +			if (mhi_chan->dir == DMA_TO_DEVICE) {
>  				atomic_dec(&mhi_cntrl->pending_pkts);
> +				/* Release the reference got from mhi_queue() */
> +				mhi_cntrl->runtime_put(mhi_cntrl);
> +			}
>  
>  			/*
>  			 * Recycle the buffer if buffer is pre-allocated,
> @@ -1021,9 +1024,11 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
>  	if (unlikely(ret))
>  		goto exit_unlock;
>  
> -	/* trigger M3 exit if necessary */
> -	if (MHI_PM_IN_SUSPEND_STATE(mhi_cntrl->pm_state))
> -		mhi_trigger_resume(mhi_cntrl);
> +	/* Packet is queued, take a usage ref to exit M3 if necessary
> +	 * for host->device buffer, balanced put is done on buffer completion
> +	 * for device->host buffer, balanced put is after ringing the DB
> +	 */
> +	mhi_cntrl->runtime_get(mhi_cntrl);
>  
>  	/* Assert dev_wake (to exit/prevent M1/M2)*/
>  	mhi_cntrl->wake_toggle(mhi_cntrl);
> @@ -1034,6 +1039,9 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
>  	if (likely(MHI_DB_ACCESS_VALID(mhi_cntrl)))
>  		mhi_ring_chan_db(mhi_cntrl, mhi_chan);
>  
> +	if (dir == DMA_FROM_DEVICE)
> +		mhi_cntrl->runtime_put(mhi_cntrl);
> +
>  exit_unlock:
>  	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
>  
> @@ -1416,8 +1424,11 @@ static void mhi_reset_data_chan(struct mhi_controller *mhi_cntrl,
>  	while (tre_ring->rp != tre_ring->wp) {
>  		struct mhi_buf_info *buf_info = buf_ring->rp;
>  
> -		if (mhi_chan->dir == DMA_TO_DEVICE)
> +		if (mhi_chan->dir == DMA_TO_DEVICE) {
>  			atomic_dec(&mhi_cntrl->pending_pkts);
> +			/* Release the reference got from mhi_queue() */
> +			mhi_cntrl->runtime_put(mhi_cntrl);
> +		}
>  
>  		if (!buf_info->pre_mapped)
>  			mhi_cntrl->unmap_single(mhi_cntrl, buf_info);
> -- 
> 2.7.4
>