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

[Alex Deucher]

On Mon, Oct 10, 2016 at 5:30 AM, Rex Zhu <Rex.Zhu at amd.com> wrote:
> Change-Id: If0f10dc8002ef8b923177cbf36d0d76316bd017c
> Signed-off-by: Rex Zhu <Rex.Zhu at amd.com>

Reviewed-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_dpm.c | 14 ++++++++------
>  1 file 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 fe36caf..14f57d9 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;
>                         }
>                 }
> --
> 1.9.1
>
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