linux-kernel - Re: [PATCH V6 15/25] MIPS: BMIPS: Flush the readahead cache after DMA

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Date:	Wed, 25 Mar 2015 10:23:58 +0100
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	Kevin Cernekee <cernekee@...il.com>
Cc:	f.fainelli@...il.com, jaedon.shin@...il.com, abrestic@...omium.org,
	tglx@...utronix.de, jason@...edaemon.net, jogo@...nwrt.org,
	arnd@...db.de, computersforpeace@...il.com,
	linux-mips@...ux-mips.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 15/25] MIPS: BMIPS: Flush the readahead cache after DMA

On Thu, Dec 25, 2014 at 09:49:10AM -0800, Kevin Cernekee wrote:

> BMIPS 3300/435x/438x CPUs have a readahead cache that is separate from
> the L1/L2.  During a DMA operation, accesses adjacent to a DMA buffer
> may cause parts of the DMA buffer to be prefetched into the RAC.  To
> avoid possible coherency problems, flush the RAC upon DMA completion.
> 
> Signed-off-by: Kevin Cernekee <cernekee@...il.com>
> Signed-off-by: Jaedon Shin <jaedon.shin@...il.com>
> ---
>  arch/mips/mm/dma-default.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
> index af5f046..38ee47a 100644
> --- a/arch/mips/mm/dma-default.c
> +++ b/arch/mips/mm/dma-default.c
> @@ -18,6 +18,7 @@
>  #include <linux/highmem.h>
>  #include <linux/dma-contiguous.h>
>  
> +#include <asm/bmips.h>
>  #include <asm/cache.h>
>  #include <asm/cpu-type.h>
>  #include <asm/io.h>

Aside of platform-specific headers having no business of getting
included directly in a generic arch file, this also breaks the build
of many platforms:

  CC      arch/mips/mm/dma-default.o
In file included from arch/mips/mm/dma-default.c:21:0:
./arch/mips/include/asm/bmips.h: In function ‘bmips_read_zscm_reg’:
./arch/mips/include/asm/bmips.h:97:160: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  cache_op(Index_Load_Tag_S, ZSCM_REG_BASE + offset);
                                                                                                                                                                ^
./arch/mips/include/asm/bmips.h: In function ‘bmips_write_zscm_reg’:
./arch/mips/include/asm/bmips.h:118:160: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
  cache_op(Index_Store_Tag_S, ZSCM_REG_BASE + offset);

I think the broken platforms are all the 64 bit platforms.

  Ralf
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