drm/amd: Flush GFXOFF requests in prepare stage

If the system hasn't entered GFXOFF when suspend starts it can cause
hangs accessing GC and RLC during the suspend stage.

Cc: <stable@vger.kernel.org> # 6.1.y: 5095d54 ("drm/amd: Evict resources during PM ops prepare() callback")
Cc: <stable@vger.kernel.org> # 6.1.y: cb11ca3 ("drm/amd: Add concept of running prepare_suspend() sequence for IP blocks")
Cc: <stable@vger.kernel.org> # 6.1.y: 2ceec37 ("drm/amd: Add missing kernel doc for prepare_suspend()")
Cc: <stable@vger.kernel.org> # 6.1.y: 3a9626c ("drm/amd: Stop evicting resources on APUs in suspend")
Cc: <stable@vger.kernel.org> # 6.6.y: 5095d54 ("drm/amd: Evict resources during PM ops prepare() callback")
Cc: <stable@vger.kernel.org> # 6.6.y: cb11ca3 ("drm/amd: Add concept of running prepare_suspend() sequence for IP blocks")
Cc: <stable@vger.kernel.org> # 6.6.y: 2ceec37 ("drm/amd: Add missing kernel doc for prepare_suspend()")
Cc: <stable@vger.kernel.org> # 6.6.y: 3a9626c ("drm/amd: Stop evicting resources on APUs in suspend")
Cc: <stable@vger.kernel.org> # 6.1+
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3132
Fixes: ab47503 ("drm/amdgpu/sdma5.2: add begin/end_use ring callbacks")
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_device.c

@@ -4539,6 +4539,8 @@ int amdgpu_device_prepare(struct drm_device *dev)
 	if (r)
 		goto unprepare;
 
+	flush_delayed_work(&adev->gfx.gfx_off_delay_work);
+
 	for (i = 0; i < adev->num_ip_blocks; i++) {
 		if (!adev->ip_blocks[i].status.valid)
 			continue;