linux-kernel - Re: [PATCH 1/5] MIPS: HIGHMEM DMA on noncoherent MIPS32 processors

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Date:	Tue, 07 Sep 2010 13:11:28 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Kevin Cernekee <cernekee@...il.com>
CC:	Ralf Baechle <ralf@...ux-mips.org>, dediao@...co.com,
	dvomlehn@...co.com, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] MIPS: HIGHMEM DMA on noncoherent MIPS32 processors

Hello.

On 07-09-2010 8:03, Kevin Cernekee wrote:

> The MIPS DMA coherency functions do not work properly (i.e. kernel oops)
> when HIGHMEM pages are passed in as arguments.  This patch uses the PPC
> approach of calling kmap_atomic() with IRQs disabled to temporarily map
> high pages, in order to flush them out to memory.

> Signed-off-by: Dezhong Diao <dediao@...co.com>
> Signed-off-by: Kevin Cernekee <cernekee@...il.com>
> ---
>   arch/mips/mm/dma-default.c |  159 ++++++++++++++++++++++----------------------
>   1 files changed, 80 insertions(+), 79 deletions(-)

> diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
> index 469d401..3f23952 100644
> --- a/arch/mips/mm/dma-default.c
> +++ b/arch/mips/mm/dma-default.c
[...]
> @@ -191,8 +231,8 @@ void dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
>   	enum dma_data_direction direction)
>   {
>   	if (cpu_is_noncoherent_r10000(dev))
> -		__dma_sync(dma_addr_to_virt(dev, dma_addr), size,
> -		           direction);
> +		__dma_sync(dma_addr_to_page(dev, dma_addr),
> +			   (dma_addr & ~PAGE_MASK), size, direction);

    Parens are not needed here.

> @@ -277,15 +297,10 @@ EXPORT_SYMBOL(dma_sync_single_for_cpu);
>   void dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
>   	size_t size, enum dma_data_direction direction)
>   {
> -	BUG_ON(direction == DMA_NONE);
> -
>   	plat_extra_sync_for_device(dev);
> -	if (!plat_device_is_coherent(dev)) {
> -		unsigned long addr;
> -
> -		addr = dma_addr_to_virt(dev, dma_handle);
> -		__dma_sync(addr, size, direction);
> -	}
> +	if (!plat_device_is_coherent(dev))
> +		__dma_sync(dma_addr_to_page(dev, dma_handle),
> +			   (dma_handle & ~PAGE_MASK), size, direction);

    Here as well...

WBR, Sergei
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