From: Tom Warren twarren@nvidia.com
According to the HW team, for some reason the normal clock select code picks what appears to be a perfectly valid 375KHz SD card clock, based on the CAR clock source and SDMMC1 controller register settings (CAR = 408MHz PLLP0 divided by 68 for 6MHz, then a SD Clock Control register divisor of 16 = 375KHz). But the resulting SD card clock, as measured by the HW team, is 700KHz, which is out-of-spec. So the WAR is to use the values given in the TRM PLLP table to generate a 400KHz SD-clock (CAR clock of 24.7MHz, SD Clock Control divisor of 62) only for SDMMC1 on T210 when the requested clock is <= 400KHz. Note that as far as I can tell, the other requests for clocks in the Tegra MMC driver result in valid SD clocks.
Signed-off-by: Tom Warren twarren@nvidia.com --- arch/arm/include/asm/arch-tegra/tegra_mmc.h | 2 +- drivers/mmc/tegra_mmc.c | 18 ++++++++++++++++++ 2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/arch/arm/include/asm/arch-tegra/tegra_mmc.h b/arch/arm/include/asm/arch-tegra/tegra_mmc.h index a8bfa46..70dcf4a 100644 --- a/arch/arm/include/asm/arch-tegra/tegra_mmc.h +++ b/arch/arm/include/asm/arch-tegra/tegra_mmc.h @@ -130,9 +130,9 @@ struct tegra_mmc { /* SDMMC1/3 settings from SDMMCx Initialization Sequence of TRM */ #define MEMCOMP_PADCTRL_VREF 7 #define AUTO_CAL_ENABLE (1 << 29) -#if defined(CONFIG_TEGRA210) #define AUTO_CAL_ACTIVE (1 << 31) #define AUTO_CAL_START (1 << 31) +#if defined(CONFIG_TEGRA210) #define AUTO_CAL_PD_OFFSET (0x7D << 8) #define AUTO_CAL_PU_OFFSET (0 << 0) #define IO_TRIM_BYPASS_MASK (1 << 2) diff --git a/drivers/mmc/tegra_mmc.c b/drivers/mmc/tegra_mmc.c index a4bd679..3ca947c 100644 --- a/drivers/mmc/tegra_mmc.c +++ b/drivers/mmc/tegra_mmc.c @@ -376,6 +376,24 @@ static void tegra_mmc_change_clock(struct tegra_mmc_priv *priv, uint clock)
rate = clk_set_rate(&priv->clk, clock); div = (rate + clock - 1) / clock; + +#if defined(CONFIG_TEGRA210) + if (priv->mmc_id == PERIPH_ID_SDMMC1 && clock <= 400000) { + /* clock_adjust_periph_pll_div() chooses a 'bad' clock + * on SDMMC1 T210, so skip it here and force a clock + * that's been spec'd in the table in the TRM for + * card-detect (400KHz). + */ + uint effective_rate = clock_adjust_periph_pll_div(priv->mmc_id, + CLOCK_ID_PERIPH, 24727273, NULL); + div = 62; + + debug("%s: WAR: Using SDMMC1 clock of %u, div %d to achieve %dHz card clock ...\n", + __func__, effective_rate, div, clock); + } else + clock_adjust_periph_pll_div(priv->mmc_id, CLOCK_ID_PERIPH, clock, + &div); +#endif debug("div = %d\n", div);
writew(0, &priv->reg->clkcon);