drm/sun4i: Add support for HDMI voltage regulator

Some boards have HDMI VCC pin connected to voltage regulator which may
not be turned on by default.

Add support for such boards by adding voltage regulator handling code to
HDMI driver.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
[Icenowy: change supply name to "hvcc"]
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180904044053.15425-11-icenowy@aosc.io

drivers/gpu/drm/sun4i/sun8i_dw_hdmi.c

@@ -125,10 +125,22 @@ static int sun8i_dw_hdmi_bind(struct device *dev, struct device *master,
 		return PTR_ERR(hdmi->clk_tmds);
 	}
 
+	hdmi->regulator = devm_regulator_get(dev, "hvcc");
+	if (IS_ERR(hdmi->regulator)) {
+		dev_err(dev, "Couldn't get regulator\n");
+		return PTR_ERR(hdmi->regulator);
+	}
+
+	ret = regulator_enable(hdmi->regulator);
+	if (ret) {
+		dev_err(dev, "Failed to enable regulator\n");
+		return ret;
+	}
+
 	ret = reset_control_deassert(hdmi->rst_ctrl);
 	if (ret) {
 		dev_err(dev, "Could not deassert ctrl reset control\n");
-		return ret;
+		goto err_disable_regulator;
 	}
 
 	ret = clk_prepare_enable(hdmi->clk_tmds);
@@ -183,6 +195,8 @@ err_disable_clk_tmds:
 	clk_disable_unprepare(hdmi->clk_tmds);
 err_assert_ctrl_reset:
 	reset_control_assert(hdmi->rst_ctrl);
+err_disable_regulator:
+	regulator_disable(hdmi->regulator);
 
 	return ret;
 }
@@ -196,6 +210,7 @@ static void sun8i_dw_hdmi_unbind(struct device *dev, struct device *master,
 	sun8i_hdmi_phy_remove(hdmi);
 	clk_disable_unprepare(hdmi->clk_tmds);
 	reset_control_assert(hdmi->rst_ctrl);
+	regulator_disable(hdmi->regulator);
 }
 
 static const struct component_ops sun8i_dw_hdmi_ops = {

drivers/gpu/drm/sun4i/sun8i_dw_hdmi.h

@@ -10,6 +10,7 @@
 #include <drm/drm_encoder.h>
 #include <linux/clk.h>
 #include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
 #include <linux/reset.h>
 
 #define SUN8I_HDMI_PHY_DBG_CTRL_REG	0x0000
@@ -176,6 +177,7 @@ struct sun8i_dw_hdmi {
 	struct drm_encoder		encoder;
 	struct sun8i_hdmi_phy		*phy;
 	struct dw_hdmi_plat_data	plat_data;
+	struct regulator		*regulator;
 	struct reset_control		*rst_ctrl;
 };