[ARM] Fix pxamci regression

Fix:

WARNING: at arch/arm/mach-pxa/clock.c:69 clk_disable()
[<c002d7c8>] (dump_stack+0x0/0x14) from [<c00334f4>] (clk_disable+0x34/0xa0)
[<c00334c0>] (clk_disable+0x0/0xa0) from [<c028a43c>] (pxamci_set_ios+0x74/0xf0)
[<c028a3c8>] (pxamci_set_ios+0x0/0xf0) from [<c0281548>] (mmc_power_off+0x90/0x9c)
[<c02814b8>] (mmc_power_off+0x0/0x9c) from [<c0281a30>] (mmc_start_host+0x18/0x28)
[<c0281a18>] (mmc_start_host+0x0/0x28) from [<c02825a0>] (mmc_add_host+0xe8/0x104)
[<c02824b8>] (mmc_add_host+0x0/0x104) from [<c028a7d0>] (pxamci_probe+0x24c/0x2f4)
[<c028a584>] (pxamci_probe+0x0/0x2f4) from [<c01e5948>] (platform_drv_probe+0x20/0x24)
...
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/mmc/host/pxamci.c

@@ -39,6 +39,7 @@
 #define DRIVER_NAME	"pxa2xx-mci"
 
 #define NR_SG	1
+#define CLKRT_OFF	(~0)
 
 struct pxamci_host {
 	struct mmc_host		*mmc;
@@ -371,6 +372,9 @@ static void pxamci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		unsigned long rate = host->clkrate;
 		unsigned int clk = rate / ios->clock;
 
+		if (host->clkrt == CLKRT_OFF)
+			clk_enable(host->clk);
+
 		/*
 		 * clk might result in a lower divisor than we
 		 * desire.  check for that condition and adjust
@@ -379,14 +383,16 @@ static void pxamci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		if (rate / clk > ios->clock)
 			clk <<= 1;
 		host->clkrt = fls(clk) - 1;
-		clk_enable(host->clk);
 
 		/*
 		 * we write clkrt on the next command
 		 */
 	} else {
 		pxamci_stop_clock(host);
-		clk_disable(host->clk);
+		if (host->clkrt != CLKRT_OFF) {
+			host->clkrt = CLKRT_OFF;
+			clk_disable(host->clk);
+		}
 	}
 
 	if (host->power_mode != ios->power_mode) {
@@ -498,6 +504,7 @@ static int pxamci_probe(struct platform_device *pdev)
 	host->mmc = mmc;
 	host->dma = -1;
 	host->pdata = pdev->dev.platform_data;
+	host->clkrt = CLKRT_OFF;
 
 	host->clk = clk_get(&pdev->dev, "MMCCLK");
 	if (IS_ERR(host->clk)) {