[alsa-devel] [PATCH] ASoC: omap-pcm: Lower the dma coherent mask to 32bits
tiwai at suse.de
Fri Dec 6 14:04:22 CET 2013
At Fri, 6 Dec 2013 12:25:43 +0000,
Russell King - ARM Linux wrote:
> On Fri, Dec 06, 2013 at 09:12:22AM +0100, Takashi Iwai wrote:
> > But, it's still unclear why only get_coherent_dma_mask() takes max_pfn
> > into account for the check of dma_to_pfn(dev, mask).
> > In dma_supported(),
> > unsigned long limit;
> > limit = dma_to_pfn(dev, mask);
> > if (limit < arm_dma_pfn_limit)
> > return 0;
> > while in get_coherent_dma_mask(),
> > unsigned long max_dma_pfn;
> > max_dma_pfn = min(max_pfn, arm_dma_pfn_limit);
> > if (dma_to_pfn(dev, mask) < max_dma_pfn)
> > return 0;
> > So, the current code looks to me that the results from
> > dma_set_coherent_mask() and the actual allocation may conflict.
> I did ask Peter to replace *both* with the same thing.
Well, I'm looking at different points. You requested Peter to test
both functions to take:
if (sizeof(mask) != sizeof(dma_addr_t) &&
mask > (dma_addr_t)~0 &&
dma_to_pfn(dev, ~0) < min(max_pfn, arm_dma_pfn_limit))
But, after that line, dma_supported() has another check:
if (dma_to_pfn(dev, mask) < arm_dma_pfn_limit)
and get_coherent_dma_mask() has a different check:
if (dma_to_pfn(dev, mask) < min(max_pfn, arm_dma_pfn_limit))
(the expressions here are expanded for easier comparison)
This is what I'm wondering.
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