MMC: DWMMC: Correct the CLKDIV register value

This patch corrects the divider value written to CLKDIV register.
Since SDCLKIN is divided inside controller by the DIVRATIO value set
in the CLKSEL register, we need to use the same output clock value to
calculate the CLKDIV value.
as per user manual: cclk_in = SDCLKIN / (DIVRATIO + 1)

Input parameter to mmc_clk is changed to dwmci_host, since
we need the same to read DWMCI_CLKSEL register.

This improves the read timing values for channel 0 on SMDK5250
from 0.288sec to 0.144sec

Signed-off-by: Rajeshwari S Shinde <rajeshwari.s@samsung.com>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>

arch/arm/include/asm/arch-exynos/dwmmc.h

@@ -23,6 +23,10 @@
 #define MPSCTRL_ENCRYPTION		(0x1<<1)
 #define MPSCTRL_VALID			(0x1<<0)
 
+/* CLKSEL Register */
+#define DWMCI_DIVRATIO_BIT		24
+#define DWMCI_DIVRATIO_MASK		0x7
+
 #ifdef CONFIG_OF_CONTROL
 int exynos_dwmmc_init(const void *blob);
 #endif

drivers/mmc/dw_mmc.c

@@ -237,7 +237,7 @@ static int dwmci_setup_bus(struct dwmci_host *host, u32 freq)
 	 * host->bus_hz should be set from user.
 	 */
 	if (host->get_mmc_clk)
-		sclk = host->get_mmc_clk(host->dev_index);
+		sclk = host->get_mmc_clk(host);
 	else if (host->bus_hz)
 		sclk = host->bus_hz;
 	else {

drivers/mmc/exynos_dw_mmc.c

@@ -29,9 +29,22 @@ static void exynos_dwmci_clksel(struct dwmci_host *host)
 	dwmci_writel(host, DWMCI_CLKSEL, host->clksel_val);
 }
 
-unsigned int exynos_dwmci_get_clk(int dev_index)
+unsigned int exynos_dwmci_get_clk(struct dwmci_host *host)
 {
-	return get_mmc_clk(dev_index);
+	unsigned long sclk;
+	int8_t clk_div;
+
+	/*
+	 * Since SDCLKIN is divided inside controller by the DIVRATIO
+	 * value set in the CLKSEL register, we need to use the same output
+	 * clock value to calculate the CLKDIV value.
+	 * as per user manual:cclk_in = SDCLKIN / (DIVRATIO + 1)
+	 */
+	clk_div = ((dwmci_readl(host, DWMCI_CLKSEL) >> DWMCI_DIVRATIO_BIT)
+			& DWMCI_DIVRATIO_MASK) + 1;
+	sclk = get_mmc_clk(host->dev_index);
+
+	return sclk / clk_div;
 }
 
 static void exynos_dwmci_board_init(struct dwmci_host *host)

include/dwmmc.h

@@ -142,7 +142,7 @@ struct dwmci_host {
 
 	void (*clksel)(struct dwmci_host *host);
 	void (*board_init)(struct dwmci_host *host);
-	unsigned int (*get_mmc_clk)(int dev_index);
+	unsigned int (*get_mmc_clk)(struct dwmci_host *host);
 };
 
 struct dwmci_idmac {