On Fri, Dec 24, 2010 at 12:20:32AM +0100, Janusz Krzysztofik wrote:
> The patch tries to implement a solution suggested by Russell King,
> http://lists.infradead.org/pipermail/linux-arm-kernel/2010-December/035264.html.
>
> It is expected to solve video buffer allocation issues for at least a
> few soc_camera I/O memory less host interface drivers, designed around
> the videobuf_dma_contig layer, which allocates video buffers using
> dma_alloc_coherent().
>
> Created against linux-2.6.37-rc5.
>
> Tested on ARM OMAP1 based Amstrad Delta with a WIP OMAP1 camera patch,
> patterned upon two mach-mx3 machine types which already try to use the
> dma_declare_coherent_memory() method for reserving a region of system
> RAM preallocated with another dma_alloc_coherent(). Compile tested for
> all modified files except arch/sh/drivers/pci/fixups-dreamcast.c.
>
> Signed-off-by: Janusz Krzysztofik <jkrzy...@tis.icnet.pl>
> ---
> I intended to quote Russell in my commit message and even asked him for
> his permission, but since he didn't respond, I decided to include a link
> to his original message only.
There's no problem quoting messages which were sent to public mailing
lists, especially when there's a record of what was said in public
archives too.
I think this is definitely a step forward.
> --- linux-2.6.37-rc5/arch/arm/mach-mx3/mach-pcm037.c.orig 2010-12-09
> 23:07:34.000000000 +0100
> +++ linux-2.6.37-rc5/arch/arm/mach-mx3/mach-pcm037.c 2010-12-23
> 18:32:24.000000000 +0100
> @@ -431,7 +431,7 @@ static int __init pcm037_camera_alloc_dm
> memset(buf, 0, buf_size);
>
> dma = dma_declare_coherent_memory(&mx3_camera.dev,
> - dma_handle, dma_handle, buf_size,
> + buf, dma_handle, buf_size,
> DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE);
>
> /* The way we call dma_declare_coherent_memory only a malloc can fail */
> --- linux-2.6.37-rc5/arch/arm/mach-mx3/mach-mx31moboard.c.orig
> 2010-12-09 23:07:34.000000000 +0100
> +++ linux-2.6.37-rc5/arch/arm/mach-mx3/mach-mx31moboard.c 2010-12-23
> 18:32:24.000000000 +0100
> @@ -486,7 +486,7 @@ static int __init mx31moboard_cam_alloc_
> memset(buf, 0, buf_size);
>
> dma = dma_declare_coherent_memory(&mx3_camera.dev,
> - dma_handle, dma_handle, buf_size,
> + buf, dma_handle, buf_size,
> DMA_MEMORY_MAP | DMA_MEMORY_EXCLUSIVE);
>
> /* The way we call dma_declare_coherent_memory only a malloc can fail */
A side note for the mx3 folk: although it's not specified in DMA-API,
memory allocated from dma_alloc_coherent() on ARM is already memset
to zero by the allocation function.
> --- linux-2.6.37-rc5/drivers/base/dma-coherent.c.orig 2010-12-09
> 23:08:03.000000000 +0100
> +++ linux-2.6.37-rc5/drivers/base/dma-coherent.c 2010-12-23
> 18:32:24.000000000 +0100
> @@ -14,10 +14,9 @@ struct dma_coherent_mem {
> unsigned long *bitmap;
> };
>
> -int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
> +int dma_declare_coherent_memory(struct device *dev, void *virt_addr,
> dma_addr_t device_addr, size_t size, int flags)
> {
> - void __iomem *mem_base = NULL;
> int pages = size >> PAGE_SHIFT;
> int bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);
>
> @@ -30,10 +29,6 @@ int dma_declare_coherent_memory(struct d
>
> /* FIXME: this routine just ignores DMA_MEMORY_INCLUDES_CHILDREN */
>
> - mem_base = ioremap(bus_addr, size);
> - if (!mem_base)
> - goto out;
> -
> dev->dma_mem = kzalloc(sizeof(struct dma_coherent_mem), GFP_KERNEL);
> if (!dev->dma_mem)
> goto out;
> @@ -41,7 +36,7 @@ int dma_declare_coherent_memory(struct d
> if (!dev->dma_mem->bitmap)
> goto free1_out;
>
> - dev->dma_mem->virt_base = mem_base;
> + dev->dma_mem->virt_base = virt_addr;
I didn't see anything changing the dev->dma_mem->virt_base type to
drop the __iomem attribute (which I suspect shouldn't be there - we're
returning it via a void pointer anyway, so I think the whole coherent
part of the DMA API should be __iomem-less.
It also pushes the sparse address space warnings to the right place
IMHO too.
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