linux-mips
[Top] [All Lists]

Re: [PATCH] MIPS: mm: Move some checks out of 'for' loop in DMA operatio

To: ralf@linux-mips.org
Subject: Re: [PATCH] MIPS: mm: Move some checks out of 'for' loop in DMA operations
From: "Jayachandran C." <jchandra@broadcom.com>
Date: Thu, 26 Sep 2013 16:06:52 +0530
Cc: linux-mips@linux-mips.org
In-reply-to: <1380114065-9761-1-git-send-email-jchandra@broadcom.com>
List-archive: <http://www.linux-mips.org/archives/linux-mips/>
List-help: <mailto:ecartis@linux-mips.org?Subject=help>
List-id: linux-mips <linux-mips.eddie.linux-mips.org>
List-owner: <mailto:ralf@linux-mips.org>
List-post: <mailto:linux-mips@linux-mips.org>
List-software: Ecartis version 1.0.0
List-subscribe: <mailto:ecartis@linux-mips.org?subject=subscribe%20linux-mips>
List-unsubscribe: <mailto:ecartis@linux-mips.org?subject=unsubscribe%20linux-mips>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1380114065-9761-1-git-send-email-jchandra@broadcom.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Sep 25, 2013 at 06:31:05PM +0530, Jayachandran C wrote:

The patch was missing the required Signed-off-by, added below.

> The check cpu_needs_post_dma_flush() in mips_dma_sync_sg_for_cpu() and
> the check !plat_device_is_coherent() in mips_dma_sync_sg_for_device()
> can be moved outside the for loop.
> 
> As a side effect, this also avoids a GCC bug that caused kernel compile
> to fail with the error:
> 
> arch/mips/mm/dma-default.c: In function 'mips_dma_sync_sg_for_cpu':
> arch/mips/mm/dma-default.c:316:1: internal compiler error: in 
> add_insn_before, at emit-rtl.c:3852
> 
> This gcc failure is seen in Code Sourcery toolchains [e.g. gcc version
> 4.7.2 (Sourcery CodeBench Lite 2012.09-99)] after commit "MIPS: Optimize
> current_cpu_type() for better code."

Signed-off-by: Jayachandran C <jchandra@broadcom.com>

> ---
>  arch/mips/mm/dma-default.c |   12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
> index e45e4b0..2e94185 100644
> --- a/arch/mips/mm/dma-default.c
> +++ b/arch/mips/mm/dma-default.c
> @@ -307,12 +307,10 @@ static void mips_dma_sync_sg_for_cpu(struct device *dev,
>  {
>       int i;
>  
> -     /* Make sure that gcc doesn't leave the empty loop body.  */
> -     for (i = 0; i < nelems; i++, sg++) {
> -             if (cpu_needs_post_dma_flush(dev))
> +     if (cpu_needs_post_dma_flush(dev))
> +             for (i = 0; i < nelems; i++, sg++)
>                       __dma_sync(sg_page(sg), sg->offset, sg->length,
>                                  direction);
> -     }
>  }
>  
>  static void mips_dma_sync_sg_for_device(struct device *dev,
> @@ -320,12 +318,10 @@ static void mips_dma_sync_sg_for_device(struct device 
> *dev,
>  {
>       int i;
>  
> -     /* Make sure that gcc doesn't leave the empty loop body.  */
> -     for (i = 0; i < nelems; i++, sg++) {
> -             if (!plat_device_is_coherent(dev))
> +     if (!plat_device_is_coherent(dev))
> +             for (i = 0; i < nelems; i++, sg++)
>                       __dma_sync(sg_page(sg), sg->offset, sg->length,
>                                  direction);
> -     }
>  }
>  
>  int mips_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)

JC.


<Prev in Thread] Current Thread [Next in Thread>