From a482f32992230d8bdae2caa72056ab7d9208d5f0 Mon Sep 17 00:00:00 2001 From: Tom Warren Date: Mon, 3 Jun 2019 16:06:34 -0700 Subject: mmc: t210: Fix 'bad' SD-card clock when doing 400KHz card detect 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 Reviewed-by: Jaehoon Chung --- drivers/mmc/tegra_mmc.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'drivers/mmc') diff --git a/drivers/mmc/tegra_mmc.c b/drivers/mmc/tegra_mmc.c index 73ac58c..2b04156 100644 --- a/drivers/mmc/tegra_mmc.c +++ b/drivers/mmc/tegra_mmc.c @@ -376,6 +376,25 @@ 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); -- cgit v1.1