On Wed, Nov 25, 2009 at 03:00:28PM -0500, David VomLehn wrote:
> Fixes for using DMA on systems where the DMA address and the physical address
> differ.
>
> Signed-off-by: Dezhong Diao <dediao@xxxxxxxxx>
> Signed-off-by: David VomLehn <dvomlehn@xxxxxxxxx>
> ---
> arch/mips/mm/dma-default.c | 22 ++++++++++++++--------
> 1 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
> index 414d7ff..eaa7fb4 100644
> --- a/arch/mips/mm/dma-default.c
> +++ b/arch/mips/mm/dma-default.c
> @@ -24,8 +24,11 @@ static inline unsigned long dma_addr_to_virt(struct device *dev,
> dma_addr_t dma_addr)
> {
> unsigned long addr = plat_dma_addr_to_phys(dev, dma_addr);
> + unsigned int offset = (dma_addr & ~PAGE_MASK);
> + struct page *pg;
>
> - return (unsigned long)phys_to_virt(addr);
> + pg = pfn_to_page(addr >> PAGE_SHIFT);
> + return (unsigned long)(page_address(pg) + offset);
So this is the core of the two patches.
It'll make I/O to kmapped pages work - but you're not supposed to do that.
The burden to perform I/O on highmem pages is on the subsystem that does
the I/O, not the DMA layer!
> }
>
> /*
> @@ -136,7 +139,6 @@ EXPORT_SYMBOL(dma_free_coherent);
> static inline void __dma_sync(unsigned long addr, size_t size,
> enum dma_data_direction direction)
> {
> -
This is the blank line the previous patch shouldn't have added.
> BUG_ON(addr < KSEG0);
>
> switch (direction) {
> @@ -197,8 +199,8 @@ int dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
> addr = (unsigned long) sg_virt(sg);
> if (!plat_device_is_coherent(dev) && (addr >= KSEG0))
> __dma_sync(addr, sg->length, direction);
> -
> - sg->dma_address = sg_phys(sg);
> + sg->dma_address = plat_map_dma_mem_page(dev, sg_page(sg)) +
> + sg->offset;
Ah, this segment undoes the damage done by the previous patch. If I apply
both and diff, the change looks like:
- sg->dma_address = plat_map_dma_mem(dev,
- (void *)addr, sg->length);
+ sg->dma_address = plat_map_dma_mem_page(dev, sg_page(sg)) +
+ sg->offset;
sg_page returns a struct page *. Adding sg->offset yields nonense. I think
you mean something like ((unsigned long) sg_page(sg)) + sg->offset.
> }
>
> return nents;
> @@ -253,7 +255,8 @@ void dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
> unsigned long addr;
>
> addr = dma_addr_to_virt(dev, dma_handle);
> - __dma_sync(addr, size, direction);
> + if (addr >= KSEG0)
> + __dma_sync(addr, size, direction);
Again this KSEG0 comparison will not work as intended on 64-bit. And on 32-bit
I don't see why it would be required. No userspace address should ever be
passed into this function.
> }
> }
>
> @@ -269,7 +272,8 @@ void dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
> unsigned long addr;
>
> addr = dma_addr_to_virt(dev, dma_handle);
> - __dma_sync(addr, size, direction);
> + if (addr >= KSEG0)
> + __dma_sync(addr, size, direction);
Ditto.
> }
> }
>
> @@ -284,7 +288,8 @@ void dma_sync_single_range_for_cpu(struct device *dev, dma_addr_t dma_handle,
> unsigned long addr;
>
> addr = dma_addr_to_virt(dev, dma_handle);
> - __dma_sync(addr + offset, size, direction);
> + if (addr >= KSEG0)
> + __dma_sync(addr + offset, size, direction);
Ditto.
> }
> }
>
> @@ -300,7 +305,8 @@ void dma_sync_single_range_for_device(struct device *dev, dma_addr_t dma_handle,
> unsigned long addr;
>
> addr = dma_addr_to_virt(dev, dma_handle);
> - __dma_sync(addr + offset, size, direction);
> + if (addr >= KSEG0)
> + __dma_sync(addr + offset, size, direction);
Ditto.
> }
> }
>
Ralf
