| Message ID | 1495621472-9323-3-git-send-email-vladimir.murzin@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, May 24, 2017 at 11:24:27AM +0100, Vladimir Murzin wrote:
> This patch adds a simple implementation of mmap to dma_noop_ops.
Currently we use dma_common_mmap as the generic fallback if a dma_ops
instance doesn't implement a mmap method. Can you just fix up
dma_common_mmap for your nommu case - it looks like yours is basically
a subset.
In fact I suspect yours should call dma_mmap_from_coherent as well,
so the only different is the lack of pgprot_noncached call.
On 20/06/17 14:23, Christoph Hellwig wrote: > On Wed, May 24, 2017 at 11:24:27AM +0100, Vladimir Murzin wrote: >> This patch adds a simple implementation of mmap to dma_noop_ops. > > Currently we use dma_common_mmap as the generic fallback if a dma_ops > instance doesn't implement a mmap method. Can you just fix up > dma_common_mmap for your nommu case - it looks like yours is basically > a subset. dma_common_map() is guarded with CONFIG_MMU and I'm not dare to change that since I have no idea 1) why it was done 2) how it affects other arches :( > > In fact I suspect yours should call dma_mmap_from_coherent as well, > so the only different is the lack of pgprot_noncached call. > OK, I'll add a call to dma_mmap_from_coherent(). Cheers Vladimir
On Thu, Jun 22, 2017 at 01:46:09PM +0100, Vladimir Murzin wrote: > On 20/06/17 14:23, Christoph Hellwig wrote: > > On Wed, May 24, 2017 at 11:24:27AM +0100, Vladimir Murzin wrote: > >> This patch adds a simple implementation of mmap to dma_noop_ops. > > > > Currently we use dma_common_mmap as the generic fallback if a dma_ops > > instance doesn't implement a mmap method. Can you just fix up > > dma_common_mmap for your nommu case - it looks like yours is basically > > a subset. > > dma_common_map() is guarded with CONFIG_MMU and I'm not dare to change that > since I have no idea 1) why it was done 2) how it affects other arches :( That's still not a good reason for duplicating it. Please instead make all the existing nommu architecture select CONFIG_ARCH_NO_COHERENT_DMA_MMAP as a prep patch, then provide an arch helper to abstract away the pgprot_noncached, then lift CONFIG_ARCH_NO_COHERENT_DMA_MMAP for arm nommu. Bonus points for lifting it elsewhere or consolidating various copy & paste versions of the function.
diff --git a/lib/dma-noop.c b/lib/dma-noop.c index ff4ef5e..0acc3f6 100644 --- a/lib/dma-noop.c +++ b/lib/dma-noop.c @@ -66,6 +66,26 @@ static int dma_noop_supported(struct device *dev, u64 mask) return 1; } +static int dma_noop_mmap(struct device *dev, struct vm_area_struct *vma, + void *cpu_addr, dma_addr_t dma_addr, size_t size, + unsigned long attrs) +{ + unsigned long user_count = vma_pages(vma); + unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT; + unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr)); + unsigned long off = vma->vm_pgoff; + int ret = -ENXIO; + + if (off < count && user_count <= (count - off)) { + ret = remap_pfn_range(vma, vma->vm_start, + pfn + off, + user_count << PAGE_SHIFT, + vma->vm_page_prot); + } + + return ret; +} + const struct dma_map_ops dma_noop_ops = { .alloc = dma_noop_alloc, .free = dma_noop_free, @@ -73,6 +93,7 @@ const struct dma_map_ops dma_noop_ops = { .map_sg = dma_noop_map_sg, .mapping_error = dma_noop_mapping_error, .dma_supported = dma_noop_supported, + .mmap = dma_noop_mmap, }; EXPORT_SYMBOL(dma_noop_ops);