linux-kernel - Re: [PATCH 2/2] dmatest: check for dma mapping error

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Date:	Fri, 14 Dec 2012 11:19:59 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andy Shevchenko <andy.shevchenko@...il.com>,
	linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Vinod Koul <vinod.koul@...el.com>
Subject: Re: [PATCH 2/2] dmatest: check for dma mapping error

On Fri, 2012-12-14 at 00:33 -0800, Andrew Morton wrote: 
> On Fri, 14 Dec 2012 09:06:03 +0200 Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> 
> > On Fri, Dec 14, 2012 at 1:34 AM, Andrew Morton
> > <akpm@...ux-foundation.org> wrote:
> > > On Mon, 10 Dec 2012 13:37:44 +0200
> > > Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> > >
> > >> We get a warning if CONFIG_DMA_API_DEBUG=y
> > >>
> > >> [   28.150631] WARNING: at lib/dma-debug.c:933 check_unmap+0x5d6/0x6ac()
> > >> [   28.157058] dw_dmac dw_dmac.0: DMA-API: device driver failed to check map error[device address=0x0000000035698305] [size=14365 bytes] [mapped as single]
> > 
> > >> --- a/drivers/dma/dmatest.c
> > >> +++ b/drivers/dma/dmatest.c
> > >> @@ -378,15 +378,35 @@ static int dmatest_func(void *data)
> > >>
> > >>                       dma_srcs[i] = dma_map_single(dev->dev, buf, len,
> > >>                                                    DMA_TO_DEVICE);
> > >> +                     ret = dma_mapping_error(dev->dev, dma_srcs[i]);
> > >> +                     if (ret) {
> > >> +                             unmap_src(dev->dev, dma_srcs, len, i);
> > >> +                             pr_warn("%s: #%u: mapping error %d with "
> > >> +                                     "src_off=0x%x len=0x%x\n",
> > >> +                                     thread_name, total_tests - 1, ret,
> > >> +                                     src_off, len);
> > >> +                             failed_tests++;
> > >> +                             continue;
> > >> +                     }
> > >
> > > The changelog and the code don't match.  Which one is out of date?
> > 
> > I'm afraid I didn't get what is wrong.
> > 
> 
> The above code will not emit the string "dw_dmac dw_dmac.0: DMA-API:
> device driver failed to check map error[device
> address=0x0000000035698305] [size=14365 bytes] [mapped as single]".
> 
> Oh I see what you did.  That string is emitted by the kernel at
> present, and the patch prevents this.  And it also emits a new warning
> if the mapping attempt failed, and that new warning wasn't described.

Ah, okay, thank you.

> I updated the changelog:

Yes, you right, the changelog in my case describes  only part of the
problem.

> : The kernel emits a warning if CONFIG_DMA_API_DEBUG=y:
> : 
> : [   28.150631] WARNING: at lib/dma-debug.c:933 check_unmap+0x5d6/0x6ac()
> : [   28.157058] dw_dmac dw_dmac.0: DMA-API: device driver failed to check map error[device address=0x0000000035698305] [size=14365 bytes] [mapped as single]
> : 
> : Fix this by adding the required checking of the dma_map_single() return
> : value.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy
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