Re: [PATCH v2] mmc: sdhi: use maximum width for the sdbuf register

[Simon Horman <horms@verge.net.au>]

On Wed, Aug 09, 2017 at 08:29:26PM +0200, Wolfram Sang wrote:
> Make use of the 64 bit sdbuf width on Renesas R-Car Gen3. If the
> registers are 8 byte apart, the width is also 64 bit. For all others,
> the width is 32 bit, even if the registers are only 16 bit apart.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Reviewed-by: Simon Horman <horms+renesas@verge.net.au>

> ---
> 
> Change since v1:
> * width calculation is now fully backwards compatible. If it is not 8 byte
>   apart (which is only on Gen3), we will always default to 32 as before.
>   Thanks to Biju Das and Simon Horman for the error reports!
> 
> Tested on a M3-W Salvator-X and H2 Lager (with both SDHI instances). On
> the Lager, I could reproduce the problem with the old patch. It is gone now!

Do you think there is any value in widening the test-coverage of this
change, f.e. to older SoCs?

>  drivers/mmc/host/renesas_sdhi_core.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c
> index dd215723fa4312..a252145097d6a5 100644
> --- a/drivers/mmc/host/renesas_sdhi_core.c
> +++ b/drivers/mmc/host/renesas_sdhi_core.c
> @@ -459,10 +459,11 @@ static int renesas_sdhi_multi_io_quirk(struct mmc_card *card,
>  
>  static void renesas_sdhi_enable_dma(struct tmio_mmc_host *host, bool enable)
>  {
> -	sd_ctrl_write16(host, CTL_DMA_ENABLE, enable ? DMA_ENABLE_DMASDRW : 0);
> +	/* Iff regs are 8 byte apart, sdbuf is 64 bit. Otherwise always 32. */
> +	int width = (host->bus_shift == 2) ? 64 : 32;
>  
> -	/* enable 32bit access if DMA mode if possibile */
> -	renesas_sdhi_sdbuf_width(host, enable ? 32 : 16);
> +	sd_ctrl_write16(host, CTL_DMA_ENABLE, enable ? DMA_ENABLE_DMASDRW : 0);
> +	renesas_sdhi_sdbuf_width(host, enable ? width : 16);
>  }
>  
>  int renesas_sdhi_probe(struct platform_device *pdev,
> -- 
> 2.11.0
>