mmc: sdhci: add quirk SDHCI_QUIRK_CLOCK_DIV_ZERO_BROKEN

adds quirk for controllers whose clock divider zero is broken,
sdhci_set_clock function will incorporate this modification.
Signed-off-by: Suneel Garapati <suneel.garapati@xilinx.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci.c

@@ -1210,6 +1210,9 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 			}
 			real_div = div;
 			div >>= 1;
+			if ((host->quirks2 & SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN)
+				&& !div && host->max_clk <= 25000000)
+				div = 1;
 		}
 	} else {
 		/* Version 2.00 divisors must be a power of 2. */

drivers/mmc/host/sdhci.h

@@ -409,6 +409,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK2_SUPPORT_SINGLE			(1<<13)
 /* Controller broken with using ACMD23 */
 #define SDHCI_QUIRK2_ACMD23_BROKEN			(1<<14)
+/* Broken Clock divider zero in controller */
+#define SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN		(1<<15)
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */