mmc: sdhci: Fix the SD clock stop sequence

According to the SDHC specification, stopping the SD Clock is by setting
the SD Clock Enable bit in the Clock Control register at 0, instead of
setting all bits at 0.

Before stopping the SD clock, we need to make sure all SD transactions
to complete, so add checking the CMD and DAT bits in the Presen State
register, before stopping the SD clock.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>

drivers/mmc/sdhci.c

@@ -286,9 +286,25 @@ static int sdhci_send_command(struct mmc *mmc, struct mmc_cmd *cmd,
 static int sdhci_set_clock(struct mmc *mmc, unsigned int clock)
 {
 	struct sdhci_host *host = mmc->priv;
-	unsigned int div, clk, timeout;
+	unsigned int div, clk, timeout, reg;
 
-	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
+	/* Wait max 20 ms */
+	timeout = 200;
+	while (sdhci_readl(host, SDHCI_PRESENT_STATE) &
+			   (SDHCI_CMD_INHIBIT | SDHCI_DATA_INHIBIT)) {
+		if (timeout == 0) {
+			printf("%s: Timeout to wait cmd & data inhibit\n",
+			       __func__);
+			return -1;
+		}
+
+		timeout--;
+		udelay(100);
+	}
+
+	reg = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+	reg &= ~SDHCI_CLOCK_CARD_EN;
+	sdhci_writew(host, reg, SDHCI_CLOCK_CONTROL);
 
 	if (clock == 0)
 		return 0;