[U-Boot] [PATCH V3 3/6] mmc: tmio: Keep generating clock when clock are enabled

[Masahiro Yamada]

On Wed, Nov 14, 2018 at 8:44 AM Marek Vasut <marek.vasut at gmail.com> wrote:
>
> The TMIO core has a feature where it can automatically disable clock output
> when the bus is not in use. While this is useful, it also interferes with
> switching the bus to 1.8V and other background tasks of the SD/MMC cards,
> which require clock to be enabled.
>
> This patch respects the mmc->clk_disable and only disables the clock when
> the MMC core requests it. Otherwise the clock are continuously generated
> on the bus.
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
> Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
> ---
>  drivers/mmc/tmio-common.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/tmio-common.c b/drivers/mmc/tmio-common.c
> index 424b60ce52..fad2816ca5 100644
> --- a/drivers/mmc/tmio-common.c
> +++ b/drivers/mmc/tmio-common.c
> @@ -612,10 +612,16 @@ static void tmio_sd_set_clk_rate(struct tmio_sd_priv *priv,
>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
>
>         tmp &= ~TMIO_SD_CLKCTL_DIV_MASK;
> -       tmp |= val | TMIO_SD_CLKCTL_OFFEN;
> +       tmp |= val;
>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
>
> -       tmp |= TMIO_SD_CLKCTL_SCLKEN;
> +       if (!mmc->clk_disable) {
> +               tmp &= ~TMIO_SD_CLKCTL_OFFEN;
> +               tmp |= TMIO_SD_CLKCTL_SCLKEN;
> +       } else {
> +               tmp |= TMIO_SD_CLKCTL_OFFEN;
> +               tmp &= ~TMIO_SD_CLKCTL_SCLKEN;
> +       }
>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
>
>         udelay(1000);



What is the point of setting TMIO_SD_CLKCTL_OFFEN
when TMIO_SD_CLKCTL_SCLKEN is unset?


Why isn't the code like this?


        if (!mmc->clk_disable)
                tmp |= TMIO_SD_CLKCTL_SCLKEN;
        else
                tmp &= ~TMIO_SD_CLKCTL_SCLKEN;

        /* Never use OFFEN because it interferes with 1.8 switching */
        tmp &= ~TMIO_SD_CLKCTL_OFFEN;

        tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);




One more thing, you wrote

        if (!mmc->clk_disable)
                ...
        else
                ...

in this patch.


Then, soon you will rewrite it to

        if (mmc->clk_disable)
                ...
        else
                ...

in another patch:

http://patchwork.ozlabs.org/patch/998542/


Noise changes.



-- 
Best Regards
Masahiro Yamada