releases/4.4.29/drm-radeon-change-vblank_time-s-calculation-method-to-reduce-computational-error.patch

   1 From 02cfb5fccb0f9f968f0e208d89d9769aa16267bc Mon Sep 17 00:00:00 2001
   2 From: Alex Deucher <alexander.deucher@amd.com>
   3 Date: Wed, 12 Oct 2016 15:28:55 -0400
   4 Subject: drm/radeon: change vblank_time's calculation method to reduce computational error.
   5
   6 From: Alex Deucher <alexander.deucher@amd.com>
   7
   8 commit 02cfb5fccb0f9f968f0e208d89d9769aa16267bc upstream.
   9
  10 Ported from Rex's amdgpu change.
  11
  12 Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
  13 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  14
  15 ---
  16  drivers/gpu/drm/radeon/r600_dpm.c |   15 ++++++++-------
  17  1 file changed, 8 insertions(+), 7 deletions(-)
  18
  19 --- a/drivers/gpu/drm/radeon/r600_dpm.c
  20 +++ b/drivers/gpu/drm/radeon/r600_dpm.c
  21 @@ -156,19 +156,20 @@ u32 r600_dpm_get_vblank_time(struct rade
  22         struct drm_device *dev = rdev->ddev;
  23         struct drm_crtc *crtc;
  24         struct radeon_crtc *radeon_crtc;
  25 -       u32 line_time_us, vblank_lines;
  26 +       u32 vblank_in_pixels;
  27         u32 vblank_time_us = 0xffffffff; /* if the displays are off, vblank time is max */
  28
  29         if (rdev->num_crtc && rdev->mode_info.mode_config_initialized) {
  30                 list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
  31                         radeon_crtc = to_radeon_crtc(crtc);
  32                         if (crtc->enabled && radeon_crtc->enabled && radeon_crtc->hw_mode.clock) {
  33 -                               line_time_us = (radeon_crtc->hw_mode.crtc_htotal * 1000) /
  34 -                                       radeon_crtc->hw_mode.clock;
  35 -                               vblank_lines = radeon_crtc->hw_mode.crtc_vblank_end -
  36 -                                       radeon_crtc->hw_mode.crtc_vdisplay +
  37 -                                       (radeon_crtc->v_border * 2);
  38 -                               vblank_time_us = vblank_lines * line_time_us;
  39 +                               vblank_in_pixels =
  40 +                                       radeon_crtc->hw_mode.crtc_htotal *
  41 +                                       (radeon_crtc->hw_mode.crtc_vblank_end -
  42 +                                        radeon_crtc->hw_mode.crtc_vdisplay +
  43 +                                        (radeon_crtc->v_border * 2));
  44 +
  45 +                               vblank_time_us = vblank_in_pixels * 1000 / radeon_crtc->hw_mode.clock;
  46                                 break;
  47                         }
  48                 }