From 6f81b2d047c59eb77cd04795a44245d6a52cdaec Mon Sep 17 00:00:00 2001
From: limingyu <limingyu@uniontech.com>
Date: Wed, 22 Apr 2020 17:01:19 +0800
Subject: [PATCH] drm/amdgpu: Init data to avoid oops while reading pp_num_states.
Git-commit: 6f81b2d047c59eb77cd04795a44245d6a52cdaec
Patch-mainline: v5.8-rc1
References: git-fixes

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
@@ -417,8 +417,11 @@ static ssize_t amdgpu_get_pp_num_states(
 		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));
+	}
 
 	buf_len = snprintf(buf, PAGE_SIZE, "states: %d\n", data.nums);
 	for (i = 0; i < data.nums; i++)