lkml.org 
[lkml]   [2008]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: 2.6.26-rc1 regression: ISA DMA broken (bisected)
At Fri, 09 May 2008 03:37:54 +0200,
Rene Herman wrote:
>
> Good day.
>
> commit 8779f2fc3b84ebb6c5181fb13d702e9944c16069
>
> "x86: don't try to allocate from DMA zone at first"
>
> breaks all of ISA DMA. Or all of ALSA ISA DMA at least. All
> ISA soundcards are silent following that commit -- no error
> messages, everything appears fine, just silence.
>
> It won't just revert due to 32/64 merge.
>
> Rene.

Thanks for catching it. Yeah, the patch looks buggy. We had an
implicit assumption that dev = NULL for ISA devices that require 24bit
DMA.

How about the patch below? It's against the latest Linus git tree.


thanks,

Takashi


[PATCH] x86: Fix dma_alloc_coherent() for ISA devices

The recent work on x86 dma_alloc_coherent() breaks the ISA DMA buffer
allocation, which is represented by "dev = NULL" and requires 24bit
DMA implicitly.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 0c37f16..c5ef1af 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -385,11 +385,13 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
if (dma_alloc_from_coherent_mem(dev, size, dma_handle, &memory))
return memory;

- if (!dev)
+ if (!dev) {
dev = &fallback_dev;
+ gfp |= GFP_DMA;
+ }
dma_mask = dev->coherent_dma_mask;
if (dma_mask == 0)
- dma_mask = DMA_32BIT_MASK;
+ dma_mask = (gfp & GFP_DMA) ? DMA_24BIT_MASK : DMA_32BIT_MASK;

/* Device not DMA able */
if (dev->dma_mask == NULL)
@@ -403,7 +405,7 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
larger than 16MB and in this case we have a chance of
finding fitting memory in the next higher zone first. If
not retry with true GFP_DMA. -AK */
- if (dma_mask <= DMA_32BIT_MASK)
+ if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
gfp |= GFP_DMA32;
#endif


\
 
 \ /
  Last update: 2008-05-09 08:09    [W:0.168 / U:0.028 seconds]
©2003-2014 Jasper Spaans. Advertise on this site