drm/msm/gpu: Fix crash when throttling GPU immediately during boot

There is a small chance that the GPU is already hot during boot. In that
case, the call to of_devfreq_cooling_register() will immediately try to
apply devfreq cooling, as seen in the following crash:

  Unable to handle kernel paging request at virtual address 0000000000014110
  pc : a6xx_gpu_busy+0x1c/0x58 [msm]
  lr : msm_devfreq_get_dev_status+0xbc/0x140 [msm]
  Call trace:
   a6xx_gpu_busy+0x1c/0x58 [msm] (P)
   devfreq_simple_ondemand_func+0x3c/0x150
   devfreq_update_target+0x44/0xd8
   qos_max_notifier_call+0x30/0x84
   blocking_notifier_call_chain+0x6c/0xa0
   pm_qos_update_target+0xd0/0x110
   freq_qos_apply+0x3c/0x74
   apply_constraint+0x88/0x148
   __dev_pm_qos_update_request+0x7c/0xcc
   dev_pm_qos_update_request+0x38/0x5c
   devfreq_cooling_set_cur_state+0x98/0xf0
   __thermal_cdev_update+0x64/0xb4
   thermal_cdev_update+0x4c/0x58
   step_wise_manage+0x1f0/0x318
   __thermal_zone_device_update+0x278/0x424
   __thermal_cooling_device_register+0x2bc/0x308
   thermal_of_cooling_device_register+0x10/0x1c
   of_devfreq_cooling_register_power+0x240/0x2bc
   of_devfreq_cooling_register+0x14/0x20
   msm_devfreq_init+0xc4/0x1a0 [msm]
   msm_gpu_init+0x304/0x574 [msm]
   adreno_gpu_init+0x1c4/0x2e0 [msm]
   a6xx_gpu_init+0x5c8/0x9c8 [msm]
   adreno_bind+0x2a8/0x33c [msm]
   ...

At this point we haven't initialized the GMU at all yet, so we cannot read
the GMU registers inside a6xx_gpu_busy(). A similar issue was fixed before
in commit 6694482a70e9 ("drm/msm: Avoid unclocked GMU register access in
6xx gpu_busy"): msm_devfreq_init() does call devfreq_suspend_device(), but
unlike msm_devfreq_suspend(), it doesn't set the df->suspended flag
accordingly. This means the df->suspended flag does not match the actual
devfreq state after initialization and msm_devfreq_get_dev_status() will
end up accessing GMU registers, causing the crash.

Fix this by setting df->suspended correctly during initialization.

Cc: stable@vger.kernel.org
Fixes: 6694482a70e9 ("drm/msm: Avoid unclocked GMU register access in 6xx gpu_busy")
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/650772/
Signed-off-by: Rob Clark <robdclark@chromium.org>

diff --git a/drivers/gpu/drm/msm/msm_gpu_devfreq.c b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
index 6970b0f7f457c8535ecfeaa705db871594ae5fc4..2e1d5c3432728cde15d91f69da22bb915588fe86 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gpu_devfreq.c
+++ b/drivers/gpu/drm/msm/msm_gpu_devfreq.c
@@ -156,6 +156,7 @@ void msm_devfreq_init(struct msm_gpu *gpu)
        priv->gpu_devfreq_config.downdifferential = 10;
 
        mutex_init(&df->lock);
+       df->suspended = true;
 
        ret = dev_pm_qos_add_request(&gpu->pdev->dev, &df->boost_freq,
                                     DEV_PM_QOS_MIN_FREQUENCY, 0);