drm/msm/mdp5: fix reading hw revision on db410c platform

Since the commit commit c6122688 ("drm/msm/mdp5: stop overriding
drvdata") reading the MDP5 hw revision on db410c will crash the board
as the MDSS_GDSC is not enabled. Revert a part of the offending commit
(moving rpm enablement) and set priv->kms earlier. This make it possible
to use pm_runtime_get_sync() during read_mdp_hw_revision(), which will
power up both the MDP5 and MDSS devices.

Fixes: c6122688 ("drm/msm/mdp5: stop overriding drvdata")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/512985/
Link: https://lore.kernel.org/r/20221125000213.252115-1-dmitry.baryshkov@linaro.orgSigned-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c

@@ -519,10 +519,9 @@ static void read_mdp_hw_revision(struct mdp5_kms *mdp5_kms,
 	struct device *dev = &mdp5_kms->pdev->dev;
 	u32 version;
 
-	/* Manually enable the MDP5, as pm runtime isn't usable yet. */
-	mdp5_enable(mdp5_kms);
+	pm_runtime_get_sync(dev);
 	version = mdp5_read(mdp5_kms, REG_MDP5_HW_VERSION);
-	mdp5_disable(mdp5_kms);
+	pm_runtime_put_sync(dev);
 
 	*major = FIELD(version, MDP5_HW_VERSION_MAJOR);
 	*minor = FIELD(version, MDP5_HW_VERSION_MINOR);
@@ -839,6 +838,12 @@ static int mdp5_init(struct platform_device *pdev, struct drm_device *dev)
 	 */
 	clk_set_rate(mdp5_kms->core_clk, 200000000);
 
+	/* set uninit-ed kms */
+	priv->kms = &mdp5_kms->base.base;
+
+	pm_runtime_enable(&pdev->dev);
+	mdp5_kms->rpm_enabled = true;
+
 	read_mdp_hw_revision(mdp5_kms, &major, &minor);
 
 	mdp5_kms->cfg = mdp5_cfg_init(mdp5_kms, major, minor);
@@ -887,12 +892,6 @@ static int mdp5_init(struct platform_device *pdev, struct drm_device *dev)
 	if (ret)
 		goto fail;
 
-	/* set uninit-ed kms */
-	priv->kms = &mdp5_kms->base.base;
-
-	pm_runtime_enable(&pdev->dev);
-	mdp5_kms->rpm_enabled = true;
-
 	return 0;
 fail:
 	if (mdp5_kms)