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Subject[PATCH v2] drm/msm: Switch ordering of runpm put vs devfreq_idle
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From: Rob Clark <robdclark@chromium.org>

I've seen a few crashes like:

CPU: 0 PID: 216 Comm: A618-worker Tainted: G W 5.4.196 #7
Hardware name: Google Wormdingler rev1+ INX panel board (DT)
pstate: 20c00009 (nzCv daif +PAN +UAO)
pc : msm_readl+0x14/0x34
lr : a6xx_gpu_busy+0x40/0x80
sp : ffffffc011b93ad0
x29: ffffffc011b93ad0 x28: ffffffe77cba3000
x27: 0000000000000001 x26: ffffffe77bb4c4ac
x25: ffffffa2f227dfa0 x24: ffffffa2f22aab28
x23: 0000000000000000 x22: ffffffa2f22bf020
x21: ffffffa2f22bf000 x20: ffffffc011b93b10
x19: ffffffc011bd4110 x18: 000000000000000e
x17: 0000000000000004 x16: 000000000000000c
x15: 000001be3a969450 x14: 0000000000000400
x13: 00000000000101d6 x12: 0000000034155555
x11: 0000000000000001 x10: 0000000000000000
x9 : 0000000100000000 x8 : ffffffc011bd4000
x7 : 0000000000000000 x6 : 0000000000000007
x5 : ffffffc01d8b38f0 x4 : 0000000000000000
x3 : 00000000ffffffff x2 : 0000000000000002
x1 : 0000000000000000 x0 : ffffffc011bd4110
Call trace:
msm_readl+0x14/0x34
a6xx_gpu_busy+0x40/0x80
msm_devfreq_get_dev_status+0x70/0x1d0
devfreq_simple_ondemand_func+0x34/0x100
update_devfreq+0x50/0xe8
qos_notifier_call+0x2c/0x64
qos_max_notifier_call+0x1c/0x2c
notifier_call_chain+0x58/0x98
__blocking_notifier_call_chain+0x74/0x84
blocking_notifier_call_chain+0x38/0x48
pm_qos_update_target+0xf8/0x19c
freq_qos_apply+0x54/0x6c
apply_constraint+0x60/0x104
__dev_pm_qos_update_request+0xb4/0x184
dev_pm_qos_update_request+0x38/0x58
msm_devfreq_idle_work+0x34/0x40
kthread_worker_fn+0x144/0x1c8
kthread+0x140/0x284
ret_from_fork+0x10/0x18
Code: f9000bf3 910003fd aa0003f3 d503201f (b9400260)
---[ end trace f6309767a42d0831 ]---

Which smells a lot like touching hw after power collapse. This seems
a bit like a race/timing issue elsewhere, as pm_runtime_get_if_in_use()
in a6xx_gpu_busy() should have kept us from touching hw if it wasn't
powered.

But, we've seen cases where the idle_work scheduled by
msm_devfreq_idle() ends up racing with the resume path. Which, again,
shouldn't be a problem other than unnecessary freq changes.

v2. Only move the runpm _put_autosuspend, and not the _mark_last_busy()

Fixes: 9bc95570175a ("drm/msm: Devfreq tuning")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20210927152928.831245-1-robdclark@gmail.com
---
drivers/gpu/drm/msm/msm_gpu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
index eb8a6663f309..244511f85044 100644
--- a/drivers/gpu/drm/msm/msm_gpu.c
+++ b/drivers/gpu/drm/msm/msm_gpu.c
@@ -672,7 +672,6 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
msm_submit_retire(submit);

pm_runtime_mark_last_busy(&gpu->pdev->dev);
- pm_runtime_put_autosuspend(&gpu->pdev->dev);

spin_lock_irqsave(&ring->submit_lock, flags);
list_del(&submit->node);
@@ -686,6 +685,8 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
msm_devfreq_idle(gpu);
mutex_unlock(&gpu->active_lock);

+ pm_runtime_put_autosuspend(&gpu->pdev->dev);
+
msm_gem_submit_put(submit);
}

--
2.36.1
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