drm/amdgpu: change vblank_time's calculation method to reduce computational error.

Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dpm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dpm.c
index fe36caf1b7d7..14f57d9915e3 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dpm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dpm.c
@@ -113,24 +113,26 @@ void amdgpu_dpm_print_ps_status(struct amdgpu_device *adev,
         printk("\n");
 }
 
+
 u32 amdgpu_dpm_get_vblank_time(struct amdgpu_device *adev)
 {
         struct drm_device *dev = adev->ddev;
         struct drm_crtc *crtc;
         struct amdgpu_crtc *amdgpu_crtc;
-        u32 line_time_us, vblank_lines;
+        u32 vblank_in_pixels;
         u32 vblank_time_us = 0xffffffff; /* if the displays are off, vblank time is max */
 
         if (adev->mode_info.num_crtc && adev->mode_info.mode_config_initialized) {
                 list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
                         amdgpu_crtc = to_amdgpu_crtc(crtc);
                         if (crtc->enabled && amdgpu_crtc->enabled && amdgpu_crtc->hw_mode.clock) {
-                                line_time_us = (amdgpu_crtc->hw_mode.crtc_htotal * 1000) /
-                                        amdgpu_crtc->hw_mode.clock;
-                                vblank_lines = amdgpu_crtc->hw_mode.crtc_vblank_end -
+                                vblank_in_pixels =
+                                        amdgpu_crtc->hw_mode.crtc_htotal *
+                                        (amdgpu_crtc->hw_mode.crtc_vblank_end -
                                         amdgpu_crtc->hw_mode.crtc_vdisplay +
-                                        (amdgpu_crtc->v_border * 2);
-                                vblank_time_us = vblank_lines * line_time_us;
+                                        (amdgpu_crtc->v_border * 2));
+
+                                vblank_time_us = vblank_in_pixels * 1000 / amdgpu_crtc->hw_mode.clock;
                                 break;
                         }
                 }