Re: [PATCH] drm/msm/mdp5: fix reading hw revision on db410c platform

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On 25/11/2022 07:45, Abhinav Kumar wrote:
On 11/24/2022 4:02 PM, Dmitry Baryshkov wrote:
Since the commit commit c6122688f265 ("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.


This is the exact concern I had even when c6122688f265 was pushed.

https://patchwork.freedesktop.org/patch/508334/#comment_917689

Was the response given that time not correct then?

Not fully correct. I did not notice, that non-rpm-enabled mdp5 node doesn't force mdss to be in the on state. (Which is strange. Maybe we are leaking pm_runtime_enable() for it somewhere.)


https://patchwork.freedesktop.org/patch/508334/#comment_917713
Fixes: c6122688f265 ("drm/msm/mdp5: stop overriding drvdata")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
  drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c | 17 ++++++++---------
  1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
index b46f983f2b46..29ae5c9613f3 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
+++ b/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)

--
With best wishes
Dmitry




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