linux-kernel - Re: [PATCH] dma: k3dma: Fix non-cyclic mode

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Date:   Tue, 18 Jul 2017 21:28:25 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Antonio Borneo <borneo.antonio@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Zhangfei Gao <zhangfei.gao@...aro.org>,
        dmaengine@...r.kernel.org
Subject: Re: [PATCH] dma: k3dma: Fix non-cyclic mode

On Mon, Jul 10, 2017 at 01:53:43PM -0700, John Stultz wrote:
> From: Antonio Borneo <borneo.antonio@...il.com>
> 
> Commit 36387a2b1f62b5c087c5fe6f0f7b23b94f722ad7 ("k3dma: Fix
> memory handling in preparation for cyclic mode") broke the
> logic around ds_run/ds_done in case of non-cyclic DMA.
> 
> This went unnoticed as the only user of k3dma was the i2s
> audio driver, but with a patch set to enable dma on SPI,
> the issue cropped up.
> 
> This patch resolves the issue by reverting part of the
> problematic commit.

Can you explain the fix here, how reverting helps around with that?
Right now am not able to comprehend the fix on this..

> This patch has been tested to ensure both audio playback and SPI
> works fine using DMA and that no memory leak is present.
> 
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Zhangfei Gao <zhangfei.gao@...aro.org>
> Cc: dmaengine@...r.kernel.org
> Signed-off-by: Antonio Borneo <borneo.antonio@...il.com>
> [jstultz: Expanded commit message a bit]
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  drivers/dma/k3dma.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/dma/k3dma.c b/drivers/dma/k3dma.c
> index 01e25c6..01d2a75 100644
> --- a/drivers/dma/k3dma.c
> +++ b/drivers/dma/k3dma.c
> @@ -223,7 +223,6 @@ static irqreturn_t k3_dma_int_handler(int irq, void *dev_id)
>  			if (c && (tc1 & BIT(i))) {
>  				spin_lock_irqsave(&c->vc.lock, flags);
>  				vchan_cookie_complete(&p->ds_run->vd);
> -				WARN_ON_ONCE(p->ds_done);
>  				p->ds_done = p->ds_run;
>  				p->ds_run = NULL;
>  				spin_unlock_irqrestore(&c->vc.lock, flags);
> @@ -274,13 +273,14 @@ static int k3_dma_start_txd(struct k3_dma_chan *c)
>  		 */
>  		list_del(&ds->vd.node);
>  
> -		WARN_ON_ONCE(c->phy->ds_run);
> -		WARN_ON_ONCE(c->phy->ds_done);

Not sure why WARN_ON should be removed?

>  		c->phy->ds_run = ds;
> +		c->phy->ds_done = NULL;
>  		/* start dma */
>  		k3_dma_set_desc(c->phy, &ds->desc_hw[0]);
>  		return 0;
>  	}
> +	c->phy->ds_run = NULL;
> +	c->phy->ds_done = NULL;
>  	return -EAGAIN;
>  }
>  
> @@ -722,11 +722,7 @@ static int k3_dma_terminate_all(struct dma_chan *chan)
>  			k3_dma_free_desc(&p->ds_run->vd);
>  			p->ds_run = NULL;
>  		}
> -		if (p->ds_done) {
> -			k3_dma_free_desc(&p->ds_done->vd);
> -			p->ds_done = NULL;
> -		}
> -
> +		p->ds_done = NULL;
>  	}
>  	spin_unlock_irqrestore(&c->vc.lock, flags);
>  	vchan_dma_desc_free_list(&c->vc, &head);
> -- 
> 2.7.4
> 

-- 
~Vinod