[PATCH 4.8 011/125] drm/amdgpu: change vblank_times calculation method to reduce computational error.

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rex Zhu <rex....@amd.com>

commit dc8184aa8621ee8048652496884d9f40d4bb407f upstream.

Signed-off-by: Rex Zhu <rex....@amd.com>
Reviewed-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/gpu/drm/amd/amdgpu/amdgpu_dpm.c |   14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

--- 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 a
        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;
                        }
                }