mmc: Support bypass mode with the get_mmc_clk() method

Some SoCs want to adjust the input clock to the DWMMC block as a way of
controlling the MMC bus clock. Update the get_mmc_clk() method to support
this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>

drivers/mmc/dw_mmc.c

@@ -266,7 +266,7 @@ static int dwmci_setup_bus(struct dwmci_host *host, u32 freq)
 	 * host->bus_hz should be set by user.
 	 */
 	if (host->get_mmc_clk)
-		sclk = host->get_mmc_clk(host);
+		sclk = host->get_mmc_clk(host, freq);
 	else if (host->bus_hz)
 		sclk = host->bus_hz;
 	else {

drivers/mmc/exynos_dw_mmc.c

@@ -39,7 +39,7 @@ static void exynos_dwmci_clksel(struct dwmci_host *host)
 	dwmci_writel(host, DWMCI_CLKSEL, priv->sdr_timing);
 }
 
-unsigned int exynos_dwmci_get_clk(struct dwmci_host *host)
+unsigned int exynos_dwmci_get_clk(struct dwmci_host *host, uint freq)
 {
 	unsigned long sclk;
 	int8_t clk_div;

include/dwmmc.h

@@ -163,7 +163,21 @@ struct dwmci_host {
 
 	void (*clksel)(struct dwmci_host *host);
 	void (*board_init)(struct dwmci_host *host);
-	unsigned int (*get_mmc_clk)(struct dwmci_host *host);
+
+	/**
+	 * Get / set a particular MMC clock frequency
+	 *
+	 * This is used to request the current clock frequency of the clock
+	 * that drives the DWMMC peripheral. The caller will then use this
+	 * information to work out the divider it needs to achieve the
+	 * required MMC bus clock frequency. If you want to handle the
+	 * clock external to DWMMC, use @freq to select the frequency and
+	 * return that value too. Then DWMMC will put itself in bypass mode.
+	 *
+	 * @host:	DWMMC host
+	 * @freq:	Frequency the host is trying to achieve
+	 */
+	unsigned int (*get_mmc_clk)(struct dwmci_host *host, uint freq);
 
 	struct mmc_config cfg;
 };