linux-kernel - Re: [PATCH 01/11] dmaengine: dw-axi-dmac: fix reading register hen runtime suspended

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Message-ID: <ZDp2JjQRkSzwx03g@xhacker>
Date:   Sat, 15 Apr 2023 18:02:14 +0800
From:   Jisheng Zhang <jszhang@...nel.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/11] dmaengine: dw-axi-dmac: fix reading register hen
 runtime suspended

On Wed, Apr 12, 2023 at 11:03:02PM +0530, Vinod Koul wrote:
> s/hen/when..? or something else
> 
> On 14-03-23, 01:04, Jisheng Zhang wrote:
> > We should runtime resume the device before calling
> > axi_chan_is_hw_enable().
> 
> why is that can you please explain..

If the device is suspended, I.E not resumed, accessing any
registers in axi_chan_is_hw_enable() will cause cpu abort.

I will add this info into commit log of v2.

> 
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> > ---
> >  drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > index 7f3a60e28e38..23a10dbdecb7 100644
> > --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> > @@ -462,13 +462,17 @@ static void dw_axi_dma_synchronize(struct dma_chan *dchan)
> >  
> >  static int dma_chan_alloc_chan_resources(struct dma_chan *dchan)
> >  {
> > +	int ret;
> >  	struct axi_dma_chan *chan = dchan_to_axi_dma_chan(dchan);
> >  
> > +	pm_runtime_get(chan->chip->dev);
> > +
> >  	/* ASSERT: channel is idle */
> >  	if (axi_chan_is_hw_enable(chan)) {
> >  		dev_err(chan2dev(chan), "%s is non-idle!\n",
> >  			axi_chan_name(chan));
> > -		return -EBUSY;
> > +		ret = -EBUSY;
> > +		goto err_busy;
> >  	}
> >  
> >  	/* LLI address must be aligned to a 64-byte boundary */
> > @@ -478,13 +482,16 @@ static int dma_chan_alloc_chan_resources(struct dma_chan *dchan)
> >  					  64, 0);
> >  	if (!chan->desc_pool) {
> >  		dev_err(chan2dev(chan), "No memory for descriptors\n");
> > -		return -ENOMEM;
> > +		ret = -ENOMEM;
> > +		goto err_busy;
> >  	}
> >  	dev_vdbg(dchan2dev(dchan), "%s: allocating\n", axi_chan_name(chan));
> >  
> > -	pm_runtime_get(chan->chip->dev);
> > -
> >  	return 0;
> > +
> > +err_busy:
> > +	pm_runtime_put(chan->chip->dev);
> > +	return ret;
> >  }
> >  
> >  static void dma_chan_free_chan_resources(struct dma_chan *dchan)
> > -- 
> > 2.39.2
> 
> -- 
> ~Vinod