diff options
| author | yangbo lu <yangbo.lu@nxp.com> | 2016-12-26 17:46:30 +0800 |
|---|---|---|
| committer | Ulf Hansson <ulf.hansson@linaro.org> | 2017-02-13 13:20:15 +0100 |
| commit | e87d2db2a2b534dad7ac0000c597b561c160880d (patch) | |
| tree | c9734f8a622d35cb2b4758779fafe56cb8a6a702 /drivers/mmc/host/sdhci-of-esdhc.c | |
| parent | c31165d7400bb1ec12291170c9c4d072d5b0ba45 (diff) | |
mmc: sdhci-of-esdhc: avoid clock glitch when frequency is changing
The eSDHC_PRSSTAT[SDSTB] bit indicates whether the internal card clock is
stable. This bit is for the host driver to poll clock status when changing
the clock frequency. It is recommended to clear eSDHC_SYSCTL[SDCLKEN]
to remove glitch on the card clock when the frequency is changing. This
patch is to disable SDCLKEN bit before changing frequency and enable it
after SDSTB bit is set.
Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Diffstat (limited to 'drivers/mmc/host/sdhci-of-esdhc.c')
| -rw-r--r-- | drivers/mmc/host/sdhci-of-esdhc.c | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c index 364f6b87a728..d3aa67142839 100644 --- a/drivers/mmc/host/sdhci-of-esdhc.c +++ b/drivers/mmc/host/sdhci-of-esdhc.c @@ -431,6 +431,7 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) struct sdhci_esdhc *esdhc = sdhci_pltfm_priv(pltfm_host); int pre_div = 1; int div = 1; + u32 timeout; u32 temp; host->mmc->actual_clock = 0; @@ -451,8 +452,8 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) } temp = sdhci_readl(host, ESDHC_SYSTEM_CONTROL); - temp &= ~(ESDHC_CLOCK_IPGEN | ESDHC_CLOCK_HCKEN | ESDHC_CLOCK_PEREN - | ESDHC_CLOCK_MASK); + temp &= ~(ESDHC_CLOCK_SDCLKEN | ESDHC_CLOCK_IPGEN | ESDHC_CLOCK_HCKEN | + ESDHC_CLOCK_PEREN | ESDHC_CLOCK_MASK); sdhci_writel(host, temp, ESDHC_SYSTEM_CONTROL); while (host->max_clk / pre_div / 16 > clock && pre_div < 256) @@ -472,7 +473,21 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock) | (div << ESDHC_DIVIDER_SHIFT) | (pre_div << ESDHC_PREDIV_SHIFT)); sdhci_writel(host, temp, ESDHC_SYSTEM_CONTROL); - mdelay(1); + + /* Wait max 20 ms */ + timeout = 20; + while (!(sdhci_readl(host, ESDHC_PRSSTAT) & ESDHC_CLOCK_STABLE)) { + if (timeout == 0) { + pr_err("%s: Internal clock never stabilised.\n", + mmc_hostname(host->mmc)); + return; + } + timeout--; + mdelay(1); + } + + temp |= ESDHC_CLOCK_SDCLKEN; + sdhci_writel(host, temp, ESDHC_SYSTEM_CONTROL); } static void esdhc_pltfm_set_bus_width(struct sdhci_host *host, int width) |