> -----Original Message----- > From: Stefan Agner [mailto:stefan@xxxxxxxx] > Sent: Thursday, July 12, 2018 4:07 PM > To: adrian.hunter@xxxxxxxxx; ulf.hansson@xxxxxxxxxx > Cc: Fabio Estevam <fabio.estevam@xxxxxxx>; Bough Chen > <haibo.chen@xxxxxxx>; A.s. Dong <aisheng.dong@xxxxxxx>; linux- > mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Stefan Agner > <stefan@xxxxxxxx> > 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.dong@xxxxxxx> Regards Dong Aisheng > > Signed-off-by: Stefan Agner <stefan@xxxxxxxx> > --- > 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 -- 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
