> -----Original Message-----
> From: Stefan Agner [mailto:ste...@agner.ch]
> Sent: Thursday, July 12, 2018 4:07 PM
> To: adrian.hun...@intel.com; ulf.hans...@linaro.org
> Cc: Fabio Estevam <fabio.este...@nxp.com>; Bough Chen
> <haibo.c...@nxp.com>; A.s. Dong <aisheng.d...@nxp.com>; linux-
> m...@vger.kernel.org; linux-kernel@vger.kernel.org; Stefan Agner
> <ste...@agner.ch>
> Subject: [PATCH v2 1/2] mmc: sdhci-esdhc-imx: disable clocks before
> changing frequency
>
> 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 changing frequency for uSDHC IP
> variants too.
Looks ok to me.
Acked-by: Dong Aisheng <aisheng.d...@nxp.com>
Regards
Dong Aisheng
>
> Signed-off-by: Stefan Agner <ste...@agner.ch>
> ---
> drivers/mmc/host/sdhci-esdhc-imx.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-
> esdhc-imx.c
> index 85fd5a8b0b6d..acacd8481473 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;
> }
>
> --
> 2.18.0
