mmc: dw_mmc: add support for RK3288

This patch focuses on clock setting for RK3288 mmc controller.

In RK3288 mmc controller, CLKDIV register can only be set 0 or 1,
and if DDR 8bit mode, CLKDIV register must be set 1.
Signed-off-by: Addy Ke <addy.ke@rock-chips.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/rockchip-dw-mshc.txt

@@ -10,12 +10,14 @@ extensions to the Synopsys Designware Mobile Storage Host Controller.
 Required Properties:
 
 * compatible: should be
-	- "rockchip,rk2928-dw-mshc": for Rockchip RK2928 and following
+	- "rockchip,rk2928-dw-mshc": for Rockchip RK2928 and following,
+							before RK3288
+	- "rockchip,rk3288-dw-mshc": for Rockchip RK3288
 
 Example:
 
 	rkdwmmc0@12200000 {
-		compatible = "rockchip,rk2928-dw-mshc";
+		compatible = "rockchip,rk3288-dw-mshc";
 		reg = <0x12200000 0x1000>;
 		interrupts = <0 75 0>;
 		#address-cells = <1>;

drivers/mmc/host/dw_mmc-pltfm.c

@@ -21,17 +21,67 @@
 #include <linux/mmc/mmc.h>
 #include <linux/mmc/dw_mmc.h>
 #include <linux/of.h>
+#include <linux/clk.h>
 
 #include "dw_mmc.h"
 #include "dw_mmc-pltfm.h"
 
+#define RK3288_CLKGEN_DIV	2
+
 static void dw_mci_pltfm_prepare_command(struct dw_mci *host, u32 *cmdr)
 {
 	*cmdr |= SDMMC_CMD_USE_HOLD_REG;
 }
 
-static const struct dw_mci_drv_data rockchip_drv_data = {
+static int dw_mci_rk3288_setup_clock(struct dw_mci *host)
+{
+	host->bus_hz /= RK3288_CLKGEN_DIV;
+
+	return 0;
+}
+
+static void dw_mci_rk3288_set_ios(struct dw_mci *host, struct mmc_ios *ios)
+{
+	int ret;
+	unsigned int cclkin;
+	u32 bus_hz;
+
+	/*
+	 * cclkin: source clock of mmc controller.
+	 * bus_hz: card interface clock generated by CLKGEN.
+	 * bus_hz = cclkin / RK3288_CLKGEN_DIV;
+	 * ios->clock = (div == 0) ? bus_hz : (bus_hz / (2 * div))
+	 *
+	 * Note: div can only be 0 or 1
+	 *       if DDR50 8bit mode(only emmc work in 8bit mode),
+	 *       div must be set 1
+	 */
+	if ((ios->bus_width == MMC_BUS_WIDTH_8) &&
+	    (ios->timing == MMC_TIMING_MMC_DDR52))
+		cclkin = 2 * ios->clock * RK3288_CLKGEN_DIV;
+	else
+		cclkin = ios->clock * RK3288_CLKGEN_DIV;
+
+	ret = clk_set_rate(host->ciu_clk, cclkin);
+	if (ret)
+		dev_warn(host->dev, "failed to set rate %uHz\n", ios->clock);
+
+	bus_hz = clk_get_rate(host->ciu_clk) / RK3288_CLKGEN_DIV;
+	if (bus_hz != host->bus_hz) {
+		host->bus_hz = bus_hz;
+		/* force dw_mci_setup_bus() */
+		host->current_speed = 0;
+	}
+}
+
+static const struct dw_mci_drv_data rk2928_drv_data = {
+	.prepare_command	= dw_mci_pltfm_prepare_command,
+};
+
+static const struct dw_mci_drv_data rk3288_drv_data = {
 	.prepare_command	= dw_mci_pltfm_prepare_command,
+	.set_ios	= dw_mci_rk3288_set_ios,
+	.setup_clock	= dw_mci_rk3288_setup_clock,
 };
 
 static const struct dw_mci_drv_data socfpga_drv_data = {
@@ -95,7 +145,9 @@ EXPORT_SYMBOL_GPL(dw_mci_pltfm_pmops);
 static const struct of_device_id dw_mci_pltfm_match[] = {
 	{ .compatible = "snps,dw-mshc", },
 	{ .compatible = "rockchip,rk2928-dw-mshc",
-		.data = &rockchip_drv_data },
+		.data = &rk2928_drv_data },
+	{ .compatible = "rockchip,rk3288-dw-mshc",
+		.data = &rk3288_drv_data },
 	{ .compatible = "altr,socfpga-dw-mshc",
 		.data = &socfpga_drv_data },
 	{},