Hi Simon
Thanks for addressing this issue.
On Wed, 20 Jun 2012, Simon Horman wrote:
> In 930f152cc9998388031af577843baae572ac8ab6 ("mmc: sh_mmcif: mmc->f_max
> should be half of the bus clock") I changed the setting of mmc->f_max from
> the bus clock to half the bus clock based on the manual for the sh7372 SoC.
>
> Inspection of sh_mmcif_clock_control() reveals that it relies on
> mmc->f_max being set to the bus speed in order to enable the supplementary
> clock, a feature that does not exist on the sh7372.
>
> Armed with this information implement the following heuristic for setting
> mmc->f_max:
>
> * Use bus clock if the supplementary clock feature is present
> - Assumed to work on the sh7757lcr board, the only board present
> in the tree which has the feature.
To be able to better understand this change: do we have access to the
sh7757 documentation and does it actually explain how the CLK_SUP_PCLK bit
in MMCIF_CE_CLK_CTRL functions? Does it actually set the MMC bus clock to
be equal to the host clock?
Thanks
Guennadi
> * Use half the bus clock otherwise
> - As per the documentation for the sh7372 SoC.
>
> Reported-by: Magnus Damm <damm@xxxxxxxxxxxxx>
> Cc: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
>
> ---
>
> Regression information:
>
> It seems likely that this resolves a regression for the sh7757lcr which was
> introduced by 930f152cc9998388031af577843baae572ac8ab6 ("mmc: sh_mmcif:
> mmc->f_max should be half of the bus clock"). However, although I have the
> hardware in question I am unsure how to exercise the code to test if there
> is a problem or not.
>
> 930f152cc9998388031af577843baae572ac8ab6 was added between the 3.3 and 3.4.
>
> Dependency information:
>
> This patch is based on Guennadi Liakhovetski's recent series
> "[PATCH 0/5 v4] mmc: sh_mmcif: clock and power updates". It should
> be trivial to rebase it on 3.5-rc3.
> ---
> drivers/mmc/host/sh_mmcif.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sh_mmcif.c b/drivers/mmc/host/sh_mmcif.c
> index f0f518b..dfcfe83 100644
> --- a/drivers/mmc/host/sh_mmcif.c
> +++ b/drivers/mmc/host/sh_mmcif.c
> @@ -919,10 +919,11 @@ static void sh_mmcif_request(struct mmc_host *mmc, struct mmc_request *mrq)
> static int sh_mmcif_clk_update(struct sh_mmcif_host *host)
> {
> int ret = clk_enable(host->hclk);
> + struct sh_mmcif_plat_data *p = host->pd->dev.platform_data;
>
> if (!ret) {
> host->clk = clk_get_rate(host->hclk);
> - host->mmc->f_max = host->clk / 2;
> + host->mmc->f_max = p->sup_pclk ? host->clk : host->clk / 2;
> host->mmc->f_min = host->clk / 512;
> }
>
> --
> 1.7.10.2.484.gcd07cc5
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
