drm/amdgpu: Init data to avoid oops while reading pp_num_states.

For chip like CHIP_OLAND with si enabled(amdgpu.si_support=1),
the amdgpu will expose pp_num_states to the /sys directory.
In this moment, read the pp_num_states file will excute the
amdgpu_get_pp_num_states func. In our case, the data hasn't
been initialized, so the kernel will access some ilegal
address, trigger the segmentfault and system will reboot soon:

    uos@uos-PC:~$ cat /sys/devices/pci0000\:00/0000\:00\:00.0/0000\:01\:00
    .0/pp_num_states

    Message from syslogd@uos-PC at Apr 22 09:26:20 ...
     kernel:[   82.154129] Internal error: Oops: 96000004 [#1] SMP

This patch aims to fix this problem, avoid that reading file
triggers the kernel sementfault.

Signed-off-by: limingyu <limingyu@uniontech.com>
Signed-off-by: zhoubinbin <zhoubinbin@uniontech.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
index abe94a5..49e2e43 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
@@ -444,8 +444,11 @@ static ssize_t amdgpu_get_pp_num_states(struct device *dev,
                ret = smu_get_power_num_states(&adev->smu, &data);
                if (ret)
                        return ret;
-       } else if (adev->powerplay.pp_funcs->get_pp_num_states)
+       } else if (adev->powerplay.pp_funcs->get_pp_num_states) {
                amdgpu_dpm_get_pp_num_states(adev, &data);
+       } else {
+               memset(&data, 0, sizeof(data));
+       }
 
        pm_runtime_mark_last_busy(ddev->dev);
        pm_runtime_put_autosuspend(ddev->dev);