From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Agner Subject: Re: [PATCH v2 1/2] mmc: sdhci-esdhc-imx: disable clocks before changing frequency Date: Thu, 12 Jul 2018 10:10:23 +0200 Message-ID: <1e00d6df032983bd588b068d30b48cea@agner.ch> References: <20180712080650.13878-1-stefan@agner.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180712080650.13878-1-stefan@agner.ch> Sender: linux-kernel-owner@vger.kernel.org To: adrian.hunter@intel.com, ulf.hansson@linaro.org Cc: fabio.estevam@nxp.com, haibo.chen@nxp.com, aisheng.dong@nxp.com, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-mmc@vger.kernel.org On 12.07.2018 10:06, Stefan Agner 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 changing frequency for uSDHC > IP variants too. Ignore this patch, its a duplicate. I should not have pressed Ctrl-C while git send-email is working :-) -- Stefan > > Signed-off-by: Stefan Agner > --- > 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; > }