[PATCH v2] drm/bridge: tc358767: Make sure Refclk clock are enabled

[Marek Vasut <marex@xxxxxxx>]

The Refclk may be supplied by SoC clock output instead of crystal
oscillator, make sure the clock are enabled before any other action
is performed with the bridge chip, otherwise it may either fail to
operate at all, or miss reset GPIO toggle.

Fixes: 7caff0fc4296e ("drm/bridge: tc358767: Add DPI to eDP bridge driver")
Signed-off-by: Marek Vasut <marex@xxxxxxx>
Cc: Jonas Karlman <jonas@xxxxxxxxx>
Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Cc: Marek Vasut <marex@xxxxxxx>
Cc: Maxime Ripard <maxime@xxxxxxxxxx>
Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
Cc: Robert Foss <robert.foss@xxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
---
V2: Use devm_add_action_or_reset() to add clock disable hook instead
    of wall of failpath
---
 drivers/gpu/drm/bridge/tc358767.c | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index 45ea829d56601..b2ef01303be23 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -2033,6 +2033,13 @@ static int tc_probe_bridge_endpoint(struct tc_data *tc)
 	return -EINVAL;
 }
 
+static void tc_clk_disable(void *data)
+{
+	struct clk *refclk = data;
+
+	clk_disable_unprepare(refclk);
+}
+
 static int tc_probe(struct i2c_client *client, const struct i2c_device_id *id)
 {
 	struct device *dev = &client->dev;
@@ -2049,6 +2056,22 @@ static int tc_probe(struct i2c_client *client, const struct i2c_device_id *id)
 	if (ret)
 		return ret;
 
+	tc->refclk = devm_clk_get(dev, "ref");
+	if (IS_ERR(tc->refclk)) {
+		ret = PTR_ERR(tc->refclk);
+		dev_err(dev, "Failed to get refclk: %d\n", ret);
+		return ret;
+	}
+
+	ret = devm_add_action_or_reset(dev, tc_clk_disable, tc->refclk);
+	if (ret)
+		return ret;
+
+	clk_prepare_enable(tc->refclk);
+
+	/* tRSTW = 100 cycles , at 13 MHz that is ~7.69 us */
+	usleep_range(10, 15);
+
 	/* Shut down GPIO is optional */
 	tc->sd_gpio = devm_gpiod_get_optional(dev, "shutdown", GPIOD_OUT_HIGH);
 	if (IS_ERR(tc->sd_gpio))
@@ -2069,13 +2092,6 @@ static int tc_probe(struct i2c_client *client, const struct i2c_device_id *id)
 		usleep_range(5000, 10000);
 	}
 
-	tc->refclk = devm_clk_get(dev, "ref");
-	if (IS_ERR(tc->refclk)) {
-		ret = PTR_ERR(tc->refclk);
-		dev_err(dev, "Failed to get refclk: %d\n", ret);
-		return ret;
-	}
-
 	tc->regmap = devm_regmap_init_i2c(client, &tc_regmap_config);
 	if (IS_ERR(tc->regmap)) {
 		ret = PTR_ERR(tc->regmap);
-- 
2.35.1