drm: sun4i_tcon: use devm_clk_get_enabled in `sun4i_tcon_init_clocks`

Smatch reports:
drivers/gpu/drm/sun4i/sun4i_tcon.c:805 sun4i_tcon_init_clocks() warn:
'tcon->clk' from clk_prepare_enable() not released on lines: 792,801.

In the function sun4i_tcon_init_clocks(), tcon->clk and tcon->sclk0 are
not disabled in the error handling, which affects the release of
these variable. Although sun4i_tcon_bind(), which calls
sun4i_tcon_init_clocks(), use sun4i_tcon_free_clocks to disable the
variables mentioned, but the error handling branch of
sun4i_tcon_init_clocks() ignores the required disable process.

To fix this issue, use the devm_clk_get_enabled to automatically
balance enable and disabled calls. As original implementation use
sun4i_tcon_free_clocks() to disable clk explicitly, we delete the
related calls and error handling that are no longer needed.

Fixes: 9026e0d1 ("drm: Add Allwinner A10 Display Engine support")
Fixes: b14e945b ("drm/sun4i: tcon: Prepare and enable TCON channel 0 clock at init")
Fixes: 8e924047 ("drm/sun4i: support TCONs without channel 1")
Fixes: 34d698f6 ("drm/sun4i: Add has_channel_0 TCON quirk")
Signed-off-by: XuDong Liu <m202071377@hust.edu.cn>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20230430112347.4689-1-m202071377@hust.edu.cn

drivers/gpu/drm/sun4i/sun4i_tcon.c

@@ -784,21 +784,19 @@ static irqreturn_t sun4i_tcon_handler(int irq, void *private)
 static int sun4i_tcon_init_clocks(struct device *dev,
 				  struct sun4i_tcon *tcon)
 {
-	tcon->clk = devm_clk_get(dev, "ahb");
+	tcon->clk = devm_clk_get_enabled(dev, "ahb");
 	if (IS_ERR(tcon->clk)) {
 		dev_err(dev, "Couldn't get the TCON bus clock\n");
 		return PTR_ERR(tcon->clk);
 	}
-	clk_prepare_enable(tcon->clk);
 
 	if (tcon->quirks->has_channel_0) {
-		tcon->sclk0 = devm_clk_get(dev, "tcon-ch0");
+		tcon->sclk0 = devm_clk_get_enabled(dev, "tcon-ch0");
 		if (IS_ERR(tcon->sclk0)) {
 			dev_err(dev, "Couldn't get the TCON channel 0 clock\n");
 			return PTR_ERR(tcon->sclk0);
 		}
 	}
-	clk_prepare_enable(tcon->sclk0);
 
 	if (tcon->quirks->has_channel_1) {
 		tcon->sclk1 = devm_clk_get(dev, "tcon-ch1");
@@ -811,12 +809,6 @@ static int sun4i_tcon_init_clocks(struct device *dev,
 	return 0;
 }
 
-static void sun4i_tcon_free_clocks(struct sun4i_tcon *tcon)
-{
-	clk_disable_unprepare(tcon->sclk0);
-	clk_disable_unprepare(tcon->clk);
-}
-
 static int sun4i_tcon_init_irq(struct device *dev,
 			       struct sun4i_tcon *tcon)
 {
@@ -1229,14 +1221,14 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
 	ret = sun4i_tcon_init_regmap(dev, tcon);
 	if (ret) {
 		dev_err(dev, "Couldn't init our TCON regmap\n");
-		goto err_free_clocks;
+		goto err_assert_reset;
 	}
 
 	if (tcon->quirks->has_channel_0) {
 		ret = sun4i_dclk_create(dev, tcon);
 		if (ret) {
 			dev_err(dev, "Couldn't create our TCON dot clock\n");
-			goto err_free_clocks;
+			goto err_assert_reset;
 		}
 	}
 
@@ -1299,8 +1291,6 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
 err_free_dclk:
 	if (tcon->quirks->has_channel_0)
 		sun4i_dclk_free(tcon);
-err_free_clocks:
-	sun4i_tcon_free_clocks(tcon);
 err_assert_reset:
 	reset_control_assert(tcon->lcd_rst);
 	return ret;
@@ -1314,7 +1304,6 @@ static void sun4i_tcon_unbind(struct device *dev, struct device *master,
 	list_del(&tcon->list);
 	if (tcon->quirks->has_channel_0)
 		sun4i_dclk_free(tcon);
-	sun4i_tcon_free_clocks(tcon);
 }
 
 static const struct component_ops sun4i_tcon_ops = {