arm/imx: fix imx6q mmc error when mounting rootfs

The following error is seen in some case when mounting rootfs from
SD/MMC cards.

  Waiting for root device /dev/mmcblk0p1...
  mmc1: host does not support reading read-only switch. assuming write-enable.
  mmc1: new high speed SDHC card at address b368
  mmcblk0: mmc1:b368 SDC   3.74 GiB
   mmcblk0: p1
  mmc1: Timeout waiting for hardware interrupt.
  mmcblk0: error -110 transferring data, sector 3678224, nr 40, cmd response 0x900, card status 0xc00
  end_request: I/O error, dev mmcblk0, sector 3678225
  Buffer I/O error on device mmcblk0p1, logical block 458754
  lost page write due to I/O error on mmcblk0p1

This patch fixes the problem by lowering the usdhc clock and correcting
watermark configuration.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Cc: Chris Ball <cjb@laptop.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 16 insertions, 1 deletions

diff --git a/arch/arm/mach-imx/clock-imx6q.c b/arch/arm/mach-imx/clock-imx6q.c
index e0b926dfeced..613a1b993bff 100644
--- a/arch/arm/mach-imx/clock-imx6q.c
+++ b/arch/arm/mach-imx/clock-imx6q.c
@@ -1139,7 +1139,7 @@ static int _clk_set_rate(struct clk *clk, unsigned long rate)
                 return -EINVAL;
 
         max_div = ((d->bm_pred >> d->bp_pred) + 1) *
-                  ((d->bm_pred >> d->bp_pred) + 1);
+                  ((d->bm_podf >> d->bp_podf) + 1);
 
         div = parent_rate / rate;
         if (div == 0)
@@ -2002,6 +2002,21 @@ int __init mx6q_clocks_init(void)
         clk_set_rate(&asrc_serial_clk, 1500000);
         clk_set_rate(&enfc_clk, 11000000);
 
+        /*
+         * Before pinctrl API is available, we have to rely on the pad
+         * configuration set up by bootloader.  For usdhc example here,
+         * u-boot sets up the pads for 49.5 MHz case, and we have to lower
+         * the usdhc clock from 198 to 49.5 MHz to match the pad configuration.
+         *
+         * FIXME: This is should be removed after pinctrl API is available.
+         * At that time, usdhc driver can call pinctrl API to change pad
+         * configuration dynamically per different usdhc clock settings.
+         */
+        clk_set_rate(&usdhc1_clk, 49500000);
+        clk_set_rate(&usdhc2_clk, 49500000);
+        clk_set_rate(&usdhc3_clk, 49500000);
+        clk_set_rate(&usdhc4_clk, 49500000);
+
         np = of_find_compatible_node(NULL, NULL, "fsl,imx6q-gpt");
         base = of_iomap(np, 0);
         WARN_ON(!base);