drm/sun4i: sun6i_mipi_dsi: Add VCC-DSI regulator support

Allwinner MIPI DSI controllers are supplied with SoC
DSI power rails via VCC-DSI pin.

Add support for this supply pin by adding voltage
regulator handling code to MIPI DSI driver.
Tested-by: Merlijn Wajer <merlijn@wizzup.org>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191003064527.15128-6-jagan@amarulasolutions.com

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c

@@ -16,6 +16,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
 #include <linux/reset.h>
 #include <linux/slab.h>
 
@@ -1099,6 +1100,12 @@ static int sun6i_dsi_probe(struct platform_device *pdev)
 		return PTR_ERR(base);
 	}
 
+	dsi->regulator = devm_regulator_get(dev, "vcc-dsi");
+	if (IS_ERR(dsi->regulator)) {
+		dev_err(dev, "Couldn't get VCC-DSI supply\n");
+		return PTR_ERR(dsi->regulator);
+	}
+
 	dsi->regs = devm_regmap_init_mmio_clk(dev, "bus", base,
 					      &sun6i_dsi_regmap_config);
 	if (IS_ERR(dsi->regs)) {
@@ -1172,6 +1179,13 @@ static int sun6i_dsi_remove(struct platform_device *pdev)
 static int __maybe_unused sun6i_dsi_runtime_resume(struct device *dev)
 {
 	struct sun6i_dsi *dsi = dev_get_drvdata(dev);
+	int err;
+
+	err = regulator_enable(dsi->regulator);
+	if (err) {
+		dev_err(dsi->dev, "failed to enable VCC-DSI supply: %d\n", err);
+		return err;
+	}
 
 	reset_control_deassert(dsi->reset);
 	clk_prepare_enable(dsi->mod_clk);
@@ -1204,6 +1218,7 @@ static int __maybe_unused sun6i_dsi_runtime_suspend(struct device *dev)
 
 	clk_disable_unprepare(dsi->mod_clk);
 	reset_control_assert(dsi->reset);
+	regulator_disable(dsi->regulator);
 
 	return 0;
 }

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h

@@ -23,6 +23,7 @@ struct sun6i_dsi {
 	struct clk		*bus_clk;
 	struct clk		*mod_clk;
 	struct regmap		*regs;
+	struct regulator	*regulator;
 	struct reset_control	*reset;
 	struct phy		*dphy;