Re: [PATCH 2/6] dma: bcm-sba-raid: Peek mbox when we are left with no free requests

[Vinod Koul <vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Wed, Jul 26, 2017 at 11:06:40AM +0530, Anup Patel wrote:
> We should peek mbox channels when we are left with no free
> sba_requests in sba_alloc_request()

and why is the world should we do that, how does that help??

> 
> Signed-off-by: Anup Patel <anup.patel-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Reviewed-by: Ray Jui <ray.jui-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> Reviewed-by: Scott Branden <scott.branden-dY08KVG/lbpWk0Htik3J/w@public.gmane.org>
> ---
>  drivers/dma/bcm-sba-raid.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
> index 6d15fed..321420b 100644
> --- a/drivers/dma/bcm-sba-raid.c
> +++ b/drivers/dma/bcm-sba-raid.c
> @@ -199,6 +199,14 @@ static inline u32 __pure sba_cmd_pq_c_mdata(u32 d, u32 b1, u32 b0)
>  
>  /* ====== General helper routines ===== */
>  
> +static void sba_peek_mchans(struct sba_device *sba)
> +{
> +	int mchan_idx;
> +
> +	for (mchan_idx = 0; mchan_idx < sba->mchans_count; mchan_idx++)
> +		mbox_client_peek_data(sba->mchans[mchan_idx]);
> +}
> +
>  static struct sba_request *sba_alloc_request(struct sba_device *sba)
>  {
>  	unsigned long flags;
> @@ -210,8 +218,17 @@ static struct sba_request *sba_alloc_request(struct sba_device *sba)
>  	if (req)
>  		list_move_tail(&req->node, &sba->reqs_alloc_list);
>  	spin_unlock_irqrestore(&sba->reqs_lock, flags);
> -	if (!req)
> +
> +	if (!req) {
> +		/*
> +		 * We have no more free requests so, we peek
> +		 * mailbox channels hoping few active requests
> +		 * would have completed which will create more
> +		 * room for new requests.
> +		 */
> +		sba_peek_mchans(sba);
>  		return NULL;
> +	}
>  
>  	req->flags = SBA_REQUEST_STATE_ALLOCED;
>  	req->first = req;
> @@ -558,17 +575,15 @@ static enum dma_status sba_tx_status(struct dma_chan *dchan,
>  				     dma_cookie_t cookie,
>  				     struct dma_tx_state *txstate)
>  {
> -	int mchan_idx;
>  	enum dma_status ret;
>  	struct sba_device *sba = to_sba_device(dchan);
>  
> -	for (mchan_idx = 0; mchan_idx < sba->mchans_count; mchan_idx++)
> -		mbox_client_peek_data(sba->mchans[mchan_idx]);
> -
>  	ret = dma_cookie_status(dchan, cookie, txstate);
>  	if (ret == DMA_COMPLETE)
>  		return ret;
>  
> +	sba_peek_mchans(sba);
> +
>  	return dma_cookie_status(dchan, cookie, txstate);
>  }
>  
> -- 
> 2.7.4
> 

-- 
~Vinod
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