mmc: atmel: Properly fix clock configuration

Timing issue occurs on eMMC not only when modifying the frequency but
also for all the switch command(CMD6). According to the MMC spec waiting
8 clocks after a switch command would be the thing to do.

This patch allows fixing CPU hang observed when trying to changing the
bus width on a eMMC on SAMA5D4.

Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Tested-by: Marek Vasut <marex@denx.de> # on DENX MA5D4EV
Acked-by: Marek Vasut <marex@denx.de>
Tested-by: Andreas Bießmann <andreas.devel@googlemail.com> # on atngw100
Acked-by: Andreas Bießmann <andreas.devel@googlemail.com>
[fixed minor checkpatch warning]
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>

diff --git a/drivers/mmc/gen_atmel_mci.c b/drivers/mmc/gen_atmel_mci.c
index da870c6..0474a15 100644 (file)
--- a/drivers/mmc/gen_atmel_mci.c
+++ b/drivers/mmc/gen_atmel_mci.c
@@ -36,6 +36,7 @@ struct atmel_mci_priv {
        struct mmc_config       cfg;
        struct atmel_mci        *mci;
        unsigned int            initialized:1;
+       unsigned int            curr_clk;
 };
 
 /* Read Atmel MCI IP version */
@@ -91,7 +92,10 @@ static void mci_set_mode(struct mmc *mmc, u32 hz, u32 blklen)
 
                }
        }
-
+       if (version >= 0x500)
+               priv->curr_clk = bus_hz / (clkdiv * 2 + clkodd + 2);
+       else
+               priv->curr_clk = (bus_hz / (clkdiv + 1)) / 2;
        blklen &= 0xfffc;
 
        mr = MMCI_BF(CLKDIV, clkdiv);
@@ -118,8 +122,6 @@ static void mci_set_mode(struct mmc *mmc, u32 hz, u32 blklen)
        if (mmc->card_caps & mmc->cfg->host_caps & MMC_MODE_HS)
                writel(MMCI_BIT(HSMODE), &mci->cfg);
 
-       udelay(50);
-
        priv->initialized = 1;
 }
 
@@ -323,6 +325,13 @@ mci_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd, struct mmc_data *data)
                }
        }
 
+       /*
+        * After the switch command, wait for 8 clocks before the next
+        * command
+        */
+       if (cmd->cmdidx == MMC_CMD_SWITCH)
+               udelay(8*1000000 / priv->curr_clk); /* 8 clk in us */
+
        return 0;
 }