After switching from mem->dma_handle to virt_to_phys(mem->vaddr) used
for obtaining page frame number passed to remap_pfn_range()
(commit 35d9f510b67b10338161aba6229d4f55b4000f5b), videobuf-dma-contig
stopped working on my ARM based board. The ARM architecture maintainer,
Russell King, confirmed that using something like
virt_to_phys(dma_alloc_coherent()) is not supported on ARM, and can be
broken on other architectures as well. The author of the change, Jiri
Slaby, also confirmed that his code may not work on all architectures.
The patch tries to solve this regression by using
virt_to_phys(bus_to_virt(mem->dma_handle)) instead of problematic
virt_to_phys(mem->vaddr). I think this should work even if those
translations would occure inaccurate for DMA addresses, since possible
errors introduced by both translations, performed in opposite
directions, should compensate.
Tested on ARM OMAP1 based Amstrad Delta board.
Signed-off-by: Janusz Krzysztofik <jkrzyszt@xxxxxxxxxxxx>
---
v1 -> v2 changes:
- drop dma_mmap_coherent() path, it may not work correctly for device
memory preallocated with dma_declare_coherent_memory().
drivers/media/video/videobuf-dma-contig.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- git/drivers/media/video/videobuf-dma-contig.c.orig 2011-04-09 00:38:45.000000000 +0200
+++ git/drivers/media/video/videobuf-dma-contig.c 2011-04-12 22:36:44.000000000 +0200
@@ -300,8 +300,8 @@ static int __videobuf_mmap_mapper(struct
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
retval = remap_pfn_range(vma, vma->vm_start,
- PFN_DOWN(virt_to_phys(mem->vaddr)),
- size, vma->vm_page_prot);
+ PFN_DOWN(virt_to_phys(bus_to_virt(mem->dma_handle))),
+ size, vma->vm_page_prot);
if (retval) {
dev_err(q->dev, "mmap: remap failed with error %d. ", retval);
dma_free_coherent(q->dev, mem->size,
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
