mmc: sdhci-of-at91: add presets setup

The controller claims to support SDR104. In fact, it only supports a
degraded SDR104 since the maximum frequency of the SD clock is 120 MHz
instead of 208 MHz.
The sdhci core is unaware of it and will compute a wrong clock divider.
We can deal with this specific case by using presets.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
index c1923c094ff612ff0cc370511343ae8c3a08b881..25f779e09d8e81e12b038157188ae446bf69eebe 100644 (file)
--- a/drivers/mmc/host/sdhci-of-at91.c
+++ b/drivers/mmc/host/sdhci-of-at91.c
@@ -18,6 +18,7 @@
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/io.h>
+#include <linux/kernel.h>
 #include <linux/mmc/host.h>
 #include <linux/mmc/slot-gpio.h>
 #include <linux/module.h>
@@ -32,6 +33,8 @@
 #define                SDMMC_CACR_CAPWREN      BIT(0)
 #define                SDMMC_CACR_KEY          (0x46 << 8)
 
+#define SDHCI_AT91_PRESET_COMMON_CONF  0x400 /* drv type B, programmable clock mode */
+
 struct sdhci_at91_priv {
        struct clk *hclock;
        struct clk *gck;
@@ -163,6 +166,7 @@ static int sdhci_at91_probe(struct platform_device *pdev)
        unsigned int                    clk_base, clk_mul;
        unsigned int                    gck_rate, real_gck_rate;
        int                             ret;
+       unsigned int                    preset_div;
 
        match = of_match_device(sdhci_at91_dt_match, &pdev->dev);
        if (!match)
@@ -230,6 +234,28 @@ static int sdhci_at91_probe(struct platform_device *pdev)
                         clk_mul, real_gck_rate);
        }
 
+       /*
+        * We have to set preset values because it depends on the clk_mul
+        * value. Moreover, SDR104 is supported in a degraded mode since the
+        * maximum sd clock value is 120 MHz instead of 208 MHz. For that
+        * reason, we need to use presets to support SDR104.
+        */
+       preset_div = DIV_ROUND_UP(real_gck_rate, 24000000) - 1;
+       writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
+              host->ioaddr + SDHCI_PRESET_FOR_SDR12);
+       preset_div = DIV_ROUND_UP(real_gck_rate, 50000000) - 1;
+       writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
+              host->ioaddr + SDHCI_PRESET_FOR_SDR25);
+       preset_div = DIV_ROUND_UP(real_gck_rate, 100000000) - 1;
+       writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
+              host->ioaddr + SDHCI_PRESET_FOR_SDR50);
+       preset_div = DIV_ROUND_UP(real_gck_rate, 120000000) - 1;
+       writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
+              host->ioaddr + SDHCI_PRESET_FOR_SDR104);
+       preset_div = DIV_ROUND_UP(real_gck_rate, 50000000) - 1;
+       writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
+              host->ioaddr + SDHCI_PRESET_FOR_DDR50);
+
        clk_prepare_enable(priv->mainck);
        clk_prepare_enable(priv->gck);