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SubjectRe: [PATCH 2/2] dmatest: check for dma mapping error
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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@gmail.com> wrote:
>
> > On Fri, Dec 14, 2012 at 1:34 AM, Andrew Morton
> > <akpm@linux-foundation.org> wrote:
> > > On Mon, 10 Dec 2012 13:37:44 +0200
> > > Andy Shevchenko <andriy.shevchenko@linux.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 Which one is out of date?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@linux.intel.com>
Intel Finland Oy


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