[PATCH v2] drm/msm/dpu: fix mismatch between power and frequency

[yuanjie yang <yuanjie.yang@oss.qualcomm.com>]

From: Yuanjie Yang <yuanjie.yang@oss.qualcomm.com>

During DPU runtime suspend, calling dev_pm_opp_set_rate(dev, 0) drops
the MMCX rail to MIN_SVS while the core clock frequency remains at its
original (highest) rate. When runtime resume re-enables the clock, this
may result in a mismatch between the rail voltage and the clock rate.

For example, in the DPU bind path, the sequence could be:
  cpu0: dev_sync_state -> rpmhpd_sync_state
  cpu1:                                     dpu_kms_hw_init
timeline 0 ------------------------------------------------> t

After rpmhpd_sync_state, the voltage performance is no longer guaranteed
to stay at the highest level. During dpu_kms_hw_init, calling
dev_pm_opp_set_rate(dev, 0) drops the voltage, causing the MMCX rail to
fall to MIN_SVS while the core clock is still at its maximum frequency.
When the power is re-enabled, only the clock is enabled, leading to a
situation where the MMCX rail is at MIN_SVS but the core clock is at its
highest rate. In this state, the rail cannot sustain the clock rate,
which may cause instability or system crash.

Remove the call to dev_pm_opp_set_rate(dev, 0) from dpu_runtime_suspend
to ensure the correct vote is restored when DPU resumes.

Fixes: b0530eb11913 ("drm/msm/dpu: Use OPP API to set clk/perf state")
Signed-off-by: Yuanjie Yang <yuanjie.yang@oss.qualcomm.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
index 449552513997..327881056dd1 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
@@ -1463,8 +1463,6 @@ static int __maybe_unused dpu_runtime_suspend(struct device *dev)
 	struct msm_drm_private *priv = platform_get_drvdata(pdev);
 	struct dpu_kms *dpu_kms = to_dpu_kms(priv->kms);
 
-	/* Drop the performance state vote */
-	dev_pm_opp_set_rate(dev, 0);
 	clk_bulk_disable_unprepare(dpu_kms->num_clocks, dpu_kms->clocks);
 
 	for (i = 0; i < dpu_kms->num_paths; i++)
-- 
2.43.0