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

[limingyu]

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

    Message from syslogd at 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 at uniontech.com>
Signed-off-by: zhoubinbin <zhoubinbin at uniontech.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
index abe94a55ecad..17de9dc60ea1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
@@ -444,8 +444,10 @@ 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);
-- 
2.20.1