mmc: dw_mmc-rockchip: Add memory clock auto-gating support

Per design recommendations, the memory clock can be gated when there
is no in-flight transfer, which helps save power. This feature is
introduced alongside internal phase support, and this patch enables it.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: shawn1221

drivers/mmc/host/dw_mmc-rockchip.c

@@ -19,6 +19,8 @@
 #define RK3288_CLKGEN_DIV		2
 #define SDMMC_TIMING_CON0		0x130
 #define SDMMC_TIMING_CON1		0x134
+#define SDMMC_MISC_CON			0x138
+#define MEM_CLK_AUTOGATE_ENABLE		BIT(5)
 #define ROCKCHIP_MMC_DELAY_SEL		BIT(10)
 #define ROCKCHIP_MMC_DEGREE_MASK	0x3
 #define ROCKCHIP_MMC_DEGREE_OFFSET	1
@@ -470,6 +472,7 @@ static int dw_mci_rk3576_parse_dt(struct dw_mci *host)
 
 static int dw_mci_rockchip_init(struct dw_mci *host)
 {
+	struct dw_mci_rockchip_priv_data *priv = host->priv;
 	int ret, i;
 
 	/* It is slot 8 on Rockchip SoCs */
@@ -494,6 +497,9 @@ static int dw_mci_rockchip_init(struct dw_mci *host)
 			dev_warn(host->dev, "no valid minimum freq: %d\n", ret);
 	}
 
+	if (priv->internal_phase)
+		mci_writel(host, MISC_CON, MEM_CLK_AUTOGATE_ENABLE);
+
 	return 0;
 }