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SubjectRe: [PATCH] MMC: at91_mci: modify cache flush routines
On Tue, 11 May 2010 19:09:53 +0200
Nicolas Ferre <nicolas.ferre@atmel.com> wrote:

> As we were using an internal dma flushing routine, this patch changes to the
> DMA API flush_kernel_dcache_page(). Driver is able to compile now.
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
> ---
> drivers/mmc/host/at91_mci.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mmc/host/at91_mci.c b/drivers/mmc/host/at91_mci.c
> index a6dd7da..813d208 100644
> --- a/drivers/mmc/host/at91_mci.c
> +++ b/drivers/mmc/host/at91_mci.c
> @@ -315,7 +315,7 @@ static void at91_mci_post_dma_read(struct at91mci_host *host)
> }
>
> kunmap_atomic(sgbuffer, KM_BIO_SRC_IRQ);
> - dmac_flush_range((void *)sgbuffer, ((void *)sgbuffer) + amount);
> + flush_kernel_dcache_page(sg_page(sg));
> data->bytes_xfered += amount;
> if (size == 0)
> break;

The flush_kernel_dcache_page() documentation specifically says that
thou shalt run flush_kernel_dcache_page() _prior_ to kunmapping the
page.

I don't know if that makes a difference in the real world, but heck why
not:

--- a/drivers/mmc/host/at91_mci.c~mmc-at91_mci-modify-cache-flush-routines-fix
+++ a/drivers/mmc/host/at91_mci.c
@@ -314,8 +314,8 @@ static void at91_mci_post_dma_read(struc
dmabuf = (unsigned *)tmpv;
}

- kunmap_atomic(sgbuffer, KM_BIO_SRC_IRQ);
flush_kernel_dcache_page(sg_page(sg));
+ kunmap_atomic(sgbuffer, KM_BIO_SRC_IRQ);
data->bytes_xfered += amount;
if (size == 0)
break;
_
However, I'm wondering why you chose flush_kernel_dcache_page() instead
of plain old flush_dcache_page(). Is this a pagecache or possibly
direct-io page we're dealing with here?



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