sdhci: Add set_clock callback and a quirk for nonstandard clocks

FSL eSDHC hosts have incompatible register map to manage the SDCLK.
This patch adds set_clock callback so that drivers could overwrite
set_clock behaviour.

Similar patch[1] was posted by Ben Dooks, though in Ben's version the
callback is named change_clock, plus the patch has some unrelated bits
that makes the patch difficult to reuse.

[1] http://lkml.org/lkml/2008/12/2/160Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

drivers/mmc/host/sdhci.c

@@ -949,6 +949,12 @@ static void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 	if (clock == host->clock)
 		return;
 
+	if (host->ops->set_clock) {
+		host->ops->set_clock(host, clock);
+		if (host->quirks & SDHCI_QUIRK_NONSTANDARD_CLOCK)
+			return;
+	}
+
 	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
 
 	if (clock == 0)

drivers/mmc/host/sdhci.h

@@ -218,6 +218,8 @@ struct sdhci_host {
 #define SDHCI_QUIRK_BROKEN_CARD_DETECTION		(1<<15)
 /* Controller reports inverted write-protect state */
 #define SDHCI_QUIRK_INVERTED_WRITE_PROTECT		(1<<16)
+/* Controller has nonstandard clock management */
+#define SDHCI_QUIRK_NONSTANDARD_CLOCK			(1<<17)
 
 	int			irq;		/* Device IRQ */
 	void __iomem *		ioaddr;		/* Mapped address */
@@ -284,6 +286,8 @@ struct sdhci_ops {
 	void		(*writeb)(struct sdhci_host *host, u8 val, int reg);
 #endif
 
+	void	(*set_clock)(struct sdhci_host *host, unsigned int clock);
+
 	int		(*enable_dma)(struct sdhci_host *host);
 	unsigned int	(*get_max_clock)(struct sdhci_host *host);
 	unsigned int	(*get_timeout_clock)(struct sdhci_host *host);