linux-kernel - Re: [PATCH 1/2] dma: shdma: fix runtime PM: clear channel buffers on reset

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Date:	Wed, 28 Mar 2012 14:25:04 +0900
From:	Paul Mundt <lethal@...ux-sh.org>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	linux-kernel@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	linux-sh@...r.kernel.org, linux-pm@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Magnus Damm <magnus.damm@...il.com>
Subject: Re: [PATCH 1/2] dma: shdma: fix runtime PM: clear channel buffers on reset

On Wed, Jan 04, 2012 at 03:34:17PM +0100, Guennadi Liakhovetski wrote:
> On platforms, supporting power domains, if the domain, containing a DMAC
> instance is powered down, the driver fails to resume correctly. On those
> platforms DMAC channels have an additional CHCLR register for clearing
> channel buffers. Using this register during runtime resume fixes the
> problem.
> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@....de>

..

> @@ -139,6 +157,10 @@ static int sh_dmae_rst(struct sh_dmae_device *shdev)
>  		dev_warn(shdev->common.dev, "Can't initialize DMAOR.\n");
>  		return -EIO;
>  	}
> +	if (shdev->pdata->dmaor_init & ~dmaor)
> +		dev_warn(shdev->common.dev,
> +			 "DMAOR=0x%x hasn't latched the initial value 0x%x.\n",
> +			 dmaor, shdev->pdata->dmaor_init);
>  	return 0;
>  }
>  
I've just hit this on SH7786, which I suspect means that I've got it
wired up incorrectly somehow. This hunk also appears completely unrelated
to the changelog, so I'm wondering what exactly it's for. If this is a
probe attempt then presumably we should be handing down an error and
-ENODEV'ing in the init path? Is it expected that this is non-fatal in
the other reset cases?
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