[PATCH 24/31] staging: mt7621-mmc: Change default transfer mode to DMA

[NeilBrown]

On Wed, Apr 18 2018, Christian Lütke-Stetzkamp wrote:

> The current default transfer is to use DMA or not depending on the
> size of the data. The upstream driver mtk-sd uses DMA all times,
> change the standard mode here to DMA for testing, if there are any
> performance problems with DMA for small data sizes. If not, the option
> for transfer mode should be removed in the future,
>
> Signed-off-by: Christian Lütke-Stetzkamp <christian at lkamp.de>
> ---
>  drivers/staging/mt7621-mmc/dbg.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/mt7621-mmc/dbg.c b/drivers/staging/mt7621-mmc/dbg.c
> index 9a1809d74ea3..0d6e21557d8f 100644
> --- a/drivers/staging/mt7621-mmc/dbg.c
> +++ b/drivers/staging/mt7621-mmc/dbg.c
> @@ -67,10 +67,10 @@ u32 dma_size[4] = {
>  };
>  
>  enum msdc_mode drv_mode[4] = {
> -	MODE_SIZE_DEP, /* using DMA or not depend on the size */
> -	MODE_SIZE_DEP,
> -	MODE_SIZE_DEP,
> -	MODE_SIZE_DEP
> +	MODE_DMA, /* using DMA always */
> +	MODE_DMA,
> +	MODE_DMA,
> +	MODE_DMA
>  };

It is interesting that this table is in "dbg.c"....
Maybe this was only really important during driver development, so that
the developers could experiment and measure... there is a /proc file
which allows the size cutoff to be changed.

On my board I can only use the mmc interface for a micro SD card, so I
cannot test small transfer sizes.  We might just need to bite the bullet
and discard this code. Maybe.

Thanks,
NeilBrown


>  
>  #if defined(MT6575_SD_DEBUG)
> -- 
> 2.16.1
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