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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Thu, 5 Jul 2018 15:09:43 +0200
Message-ID: <CAPDyKFrHH2Hm+Z1DgJiSunFwaC_yed_oVp82Y0dw7UMAhAq3+w@mail.gmail.com>
Subject: Re: [PATCH] mmc: sdhci-esdhc-imx: disable clocks before changing frequency
To:     Stefan Agner <stefan@agner.ch>
Cc:     Adrian Hunter <adrian.hunter@intel.com>, marcel@ziswiler.com,
        "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On 5 July 2018 at 14:15, Stefan Agner <stefan@agner.ch> wrote:
> In the uSDHC case (e.g. i.MX 6) clocks only get disabled if frequency
> is set to 0. However, it could be that the stack asks for a frequency
> change while clocks are on. In that case the function clears the
> divider registers (by clearing ESDHC_CLOCK_MASK) while the clock is
> enabled! This causes a short period of time where the clock is
> undivided (on a i.MX 6DL a clock of 196MHz has been measured).
>
> For older IP variants the driver disables clock by clearing some bits
> in ESDHC_SYSTEM_CONTROL.
>
> Make sure to disable card clock before chainging frequency for uSDHC
> IP variants too. Also fix indent to make disable/enable clock look
> alike.
>
> Signed-off-by: Stefan Agner <stefan@agner.ch>

Thanks, applied for next!

Please tell if you want this for fixes and if I should add a stable tag.

Kind regards
Uffe

> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 85fd5a8b0b6d..aa48f4b2541a 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -708,14 +708,14 @@ static inline void esdhc_pltfm_set_clock(struct sdhci_host *host,
>         int div = 1;
>         u32 temp, val;
>
> +       if (esdhc_is_usdhc(imx_data)) {
> +               val = readl(host->ioaddr + ESDHC_VENDOR_SPEC);
> +               writel(val & ~ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
> +                       host->ioaddr + ESDHC_VENDOR_SPEC);
> +       }
> +
>         if (clock == 0) {
>                 host->mmc->actual_clock = 0;
> -
> -               if (esdhc_is_usdhc(imx_data)) {
> -                       val = readl(host->ioaddr + ESDHC_VENDOR_SPEC);
> -                       writel(val & ~ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
> -                                       host->ioaddr + ESDHC_VENDOR_SPEC);
> -               }
>                 return;
>         }
>
> @@ -761,7 +761,7 @@ static inline void esdhc_pltfm_set_clock(struct sdhci_host *host,
>         if (esdhc_is_usdhc(imx_data)) {
>                 val = readl(host->ioaddr + ESDHC_VENDOR_SPEC);
>                 writel(val | ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
> -               host->ioaddr + ESDHC_VENDOR_SPEC);
> +                       host->ioaddr + ESDHC_VENDOR_SPEC);
>         }
>
>         mdelay(1);
> --
> 2.18.0
>