[PATCH v2 1/2] drm/bridge: sii902x: Enable I/O and core VCC supplies if present

[Alexandru Gagniuc <mr.nuke.me@gmail.com>]

On the SII9022, the IOVCC and CVCC12 supplies must reach the correct
voltage before the reset sequence is initiated. On most boards, this
assumption is true at boot-up, so initialization succeeds.

However, when we try to initialize the chip with incorrect supply
voltages, it will not respond to I2C requests. sii902x_probe() fails
with -ENXIO.

To resolve this, look for the "iovcc" and "cvcc12" regulators, and
make sure they are enabled before starting the reset sequence. If
these supplies are not available in devicetree, then they will default
to dummy-regulator. In that case everything will work like before.

This was observed on a STM32MP157C-DK2 booting in u-boot falcon mode.
On this board, the supplies would be set by the second stage
bootloader, which does not run in falcon mode.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
---
Changes since v1:
  * Fix return code after regulator_enable(sii902x->iovcc) fails (Fabio Estevam)
  * Use dev_err_probe() instead of dev_err() where appropriate (Sam Ravnborg)

 drivers/gpu/drm/bridge/sii902x.c | 54 ++++++++++++++++++++++++++++----
 1 file changed, 48 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
index 33fd33f953ec..d15e9f2c0d8a 100644
--- a/drivers/gpu/drm/bridge/sii902x.c
+++ b/drivers/gpu/drm/bridge/sii902x.c
@@ -17,6 +17,7 @@
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
 #include <linux/clk.h>
 
 #include <drm/drm_atomic_helper.h>
@@ -168,6 +169,8 @@ struct sii902x {
 	struct drm_connector connector;
 	struct gpio_desc *reset_gpio;
 	struct i2c_mux_core *i2cmux;
+	struct regulator *iovcc;
+	struct regulator *cvcc12;
 	/*
 	 * Mutex protects audio and video functions from interfering
 	 * each other, by keeping their i2c command sequences atomic.
@@ -954,13 +957,13 @@ static const struct drm_bridge_timings default_sii902x_timings = {
 		 | DRM_BUS_FLAG_DE_HIGH,
 };
 
+static int sii902x_init(struct sii902x *sii902x);
+
 static int sii902x_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
 	struct device *dev = &client->dev;
-	unsigned int status = 0;
 	struct sii902x *sii902x;
-	u8 chipid[4];
 	int ret;
 
 	ret = i2c_check_functionality(client->adapter,
@@ -989,6 +992,43 @@ static int sii902x_probe(struct i2c_client *client,
 
 	mutex_init(&sii902x->mutex);
 
+	sii902x->iovcc = devm_regulator_get(dev, "iovcc");
+	if (IS_ERR(sii902x->iovcc))
+		return PTR_ERR(sii902x->iovcc);
+
+	sii902x->cvcc12 = devm_regulator_get(dev, "cvcc12");
+	if (IS_ERR(sii902x->cvcc12))
+		return PTR_ERR(sii902x->cvcc12);
+
+	ret = regulator_enable(sii902x->iovcc);
+	if (ret < 0) {
+		dev_err_probe(dev, ret, "Failed to enable iovcc supply");
+		return ret;
+	}
+
+	ret = regulator_enable(sii902x->cvcc12);
+	if (ret < 0) {
+		dev_err_probe(dev, ret, "Failed to enable cvcc12 supply");
+		regulator_disable(sii902x->iovcc);
+		return ret;
+	}
+
+	ret = sii902x_init(sii902x);
+	if (ret < 0) {
+		regulator_disable(sii902x->cvcc12);
+		regulator_disable(sii902x->iovcc);
+	}
+
+	return ret;
+}
+
+static int sii902x_init(struct sii902x *sii902x)
+{
+	struct device *dev = &sii902x->i2c->dev;
+	unsigned int status = 0;
+	u8 chipid[4];
+	int ret;
+
 	sii902x_reset(sii902x);
 
 	ret = regmap_write(sii902x->regmap, SII902X_REG_TPI_RQB, 0x0);
@@ -1012,11 +1052,11 @@ static int sii902x_probe(struct i2c_client *client,
 	regmap_read(sii902x->regmap, SII902X_INT_STATUS, &status);
 	regmap_write(sii902x->regmap, SII902X_INT_STATUS, status);
 
-	if (client->irq > 0) {
+	if (sii902x->i2c->irq > 0) {
 		regmap_write(sii902x->regmap, SII902X_INT_ENABLE,
 			     SII902X_HOTPLUG_EVENT);
 
-		ret = devm_request_threaded_irq(dev, client->irq, NULL,
+		ret = devm_request_threaded_irq(dev, sii902x->i2c->irq, NULL,
 						sii902x_interrupt,
 						IRQF_ONESHOT, dev_name(dev),
 						sii902x);
@@ -1031,9 +1071,9 @@ static int sii902x_probe(struct i2c_client *client,
 
 	sii902x_audio_codec_init(sii902x, dev);
 
-	i2c_set_clientdata(client, sii902x);
+	i2c_set_clientdata(sii902x->i2c, sii902x);
 
-	sii902x->i2cmux = i2c_mux_alloc(client->adapter, dev,
+	sii902x->i2cmux = i2c_mux_alloc(sii902x->i2c->adapter, dev,
 					1, 0, I2C_MUX_GATE,
 					sii902x_i2c_bypass_select,
 					sii902x_i2c_bypass_deselect);
@@ -1051,6 +1091,8 @@ static int sii902x_remove(struct i2c_client *client)
 
 	i2c_mux_del_adapters(sii902x->i2cmux);
 	drm_bridge_remove(&sii902x->bridge);
+	regulator_disable(sii902x->cvcc12);
+	regulator_disable(sii902x->iovcc);
 
 	return 0;
 }
-- 
2.25.4