gpu: cdns-mhdp8546: fix call balance of mhdp->clk handling routines

[ Upstream commit f65727b ]

If the clock mhdp->clk was not enabled in cdns_mhdp_probe(), it should not
be disabled in any path.

The return value of clk_prepare_enable() is not checked. If mhdp->clk was
not enabled, it may be disabled in the error path of cdns_mhdp_probe()
(e.g., if cdns_mhdp_load_firmware() fails) or in cdns_mhdp_remove() after
a successful cdns_mhdp_probe() call.

Use the devm_clk_get_enabled() helper function to ensure proper call
balance for mhdp->clk.

Found by Linux Verification Center (linuxtesting.org) with Klever.

Fixes: fb43aa0 ("drm: bridge: Add support for Cadence MHDP8546 DPI/DP bridge")
Signed-off-by: Vitalii Mordan <mordan@ispras.ru>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250214154632.1907425-1-mordan@ispras.ru
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: vmordan

drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c

@@ -2463,9 +2463,9 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
 	if (!mhdp)
 		return -ENOMEM;
 
-	clk = devm_clk_get(dev, NULL);
+	clk = devm_clk_get_enabled(dev, NULL);
 	if (IS_ERR(clk)) {
-		dev_err(dev, "couldn't get clk: %ld\n", PTR_ERR(clk));
+		dev_err(dev, "couldn't get and enable clk: %ld\n", PTR_ERR(clk));
 		return PTR_ERR(clk);
 	}
 
@@ -2504,14 +2504,12 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
 
 	mhdp->info = of_device_get_match_data(dev);
 
-	clk_prepare_enable(clk);
-
 	pm_runtime_enable(dev);
 	ret = pm_runtime_resume_and_get(dev);
 	if (ret < 0) {
 		dev_err(dev, "pm_runtime_resume_and_get failed\n");
 		pm_runtime_disable(dev);
-		goto clk_disable;
+		return ret;
 	}
 
 	if (mhdp->info && mhdp->info->ops && mhdp->info->ops->init) {
@@ -2590,8 +2588,6 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
 runtime_put:
 	pm_runtime_put_sync(dev);
 	pm_runtime_disable(dev);
-clk_disable:
-	clk_disable_unprepare(mhdp->clk);
 
 	return ret;
 }
@@ -2632,8 +2628,6 @@ static void cdns_mhdp_remove(struct platform_device *pdev)
 	cancel_work_sync(&mhdp->modeset_retry_work);
 	flush_work(&mhdp->hpd_work);
 	/* Ignoring mhdp->hdcp.check_work and mhdp->hdcp.prop_work here. */
-
-	clk_disable_unprepare(mhdp->clk);
 }
 
 static const struct of_device_id mhdp_ids[] = {