pinctrl: rockchip: save and restore gpio6_c6 pinmux in suspend/resume

Save and restore the gpio6_c6 pinmux setting, since Maskrom of RK3288
would modify it to sdmmc0_det, so it need to be restored to the correct
setting after resume from Maskrom.
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Tested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/pinctrl/pinctrl-rockchip.c

@@ -1796,16 +1796,44 @@ static struct rockchip_pin_ctrl *rockchip_pinctrl_get_soc_data(
 	return ctrl;
 }
 
+#define RK3288_GRF_GPIO6C_IOMUX		0x64
+#define GPIO6C6_SEL_WRITE_ENABLE	BIT(28)
+
+static u32 rk3288_grf_gpio6c_iomux;
+
 static int __maybe_unused rockchip_pinctrl_suspend(struct device *dev)
 {
 	struct rockchip_pinctrl *info = dev_get_drvdata(dev);
+	int ret = pinctrl_force_sleep(info->pctl_dev);
+
+	if (ret)
+		return ret;
+
+	/*
+	 * RK3288 GPIO6_C6 mux would be modified by Maskrom when resume, so save
+	 * the setting here, and restore it at resume.
+	 */
+	if (info->ctrl->type == RK3288) {
+		ret = regmap_read(info->regmap_base, RK3288_GRF_GPIO6C_IOMUX,
+				  &rk3288_grf_gpio6c_iomux);
+		if (ret) {
+			pinctrl_force_default(info->pctl_dev);
+			return ret;
+		}
+	}
 
-	return pinctrl_force_sleep(info->pctl_dev);
+	return 0;
 }
 
 static int __maybe_unused rockchip_pinctrl_resume(struct device *dev)
 {
 	struct rockchip_pinctrl *info = dev_get_drvdata(dev);
+	int ret = regmap_write(info->regmap_base, RK3288_GRF_GPIO6C_IOMUX,
+			       rk3288_grf_gpio6c_iomux |
+			       GPIO6C6_SEL_WRITE_ENABLE);
+
+	if (ret)
+		return ret;
 
 	return pinctrl_force_default(info->pctl_dev);
 }