[PATCH] drm/radeon: avoid turning off spread spectrum for used pll

[Alex Deucher]

On Fri, Aug 17, 2012 at 2:40 PM,  <j.glisse at gmail.com> wrote:
> From: Jerome Glisse <jglisse at redhat.com>
>
> If spread spectrum is enabled and in use for a given pll we
> should not turn it off as it will lead to turning off display
> for crtc that use the pll (this behavior was observed on chelsea
> edp).
>
> Signed-off-by: Jerome Glisse <jglisse at redhat.com>

Looks good.  I think an alternative would be to just always enable SS
for DP/eDP rather than checking the DPCD since all DP connections run
on the same PLL.  IIRC, that's what the closed driver does.

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

> ---
>  drivers/gpu/drm/radeon/atombios_crtc.c |   25 +++++++++++++++++++++----
>  1 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c b/drivers/gpu/drm/radeon/atombios_crtc.c
> index c6fcb5b..cb18813 100644
> --- a/drivers/gpu/drm/radeon/atombios_crtc.c
> +++ b/drivers/gpu/drm/radeon/atombios_crtc.c
> @@ -444,11 +444,28 @@ union atom_enable_ss {
>  static void atombios_crtc_program_ss(struct radeon_device *rdev,
>                                      int enable,
>                                      int pll_id,
> +                                    int crtc_id,
>                                      struct radeon_atom_ss *ss)
>  {
> +       unsigned i;
>         int index = GetIndexIntoMasterTable(COMMAND, EnableSpreadSpectrumOnPPLL);
>         union atom_enable_ss args;
>
> +       if (!enable) {
> +               for (i = 0; i < 6; i++) {
> +                       if (rdev->mode_info.crtcs[i] &&
> +                           rdev->mode_info.crtcs[i]->enabled &&
> +                           i != crtc_id &&
> +                           pll_id == rdev->mode_info.crtcs[i]->pll_id) {
> +                               /* one other crtc is using this pll don't turn
> +                                * off spread spectrum as it might turn off
> +                                * display on active crtc
> +                                */
> +                               return;
> +                       }
> +               }
> +       }
> +
>         memset(&args, 0, sizeof(args));
>
>         if (ASIC_IS_DCE5(rdev)) {
> @@ -1028,7 +1045,7 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
>                 radeon_compute_pll_legacy(pll, adjusted_clock, &pll_clock, &fb_div, &frac_fb_div,
>                                           &ref_div, &post_div);
>
> -       atombios_crtc_program_ss(rdev, ATOM_DISABLE, radeon_crtc->pll_id, &ss);
> +       atombios_crtc_program_ss(rdev, ATOM_DISABLE, radeon_crtc->pll_id, radeon_crtc->crtc_id, &ss);
>
>         atombios_crtc_program_pll(crtc, radeon_crtc->crtc_id, radeon_crtc->pll_id,
>                                   encoder_mode, radeon_encoder->encoder_id, mode->clock,
> @@ -1051,7 +1068,7 @@ static void atombios_crtc_set_pll(struct drm_crtc *crtc, struct drm_display_mode
>                         ss.step = step_size;
>                 }
>
> -               atombios_crtc_program_ss(rdev, ATOM_ENABLE, radeon_crtc->pll_id, &ss);
> +               atombios_crtc_program_ss(rdev, ATOM_ENABLE, radeon_crtc->pll_id, radeon_crtc->crtc_id, &ss);
>         }
>  }
>
> @@ -1572,11 +1589,11 @@ void radeon_atom_disp_eng_pll_init(struct radeon_device *rdev)
>                                                                    ASIC_INTERNAL_SS_ON_DCPLL,
>                                                                    rdev->clock.default_dispclk);
>                 if (ss_enabled)
> -                       atombios_crtc_program_ss(rdev, ATOM_DISABLE, ATOM_DCPLL, &ss);
> +                       atombios_crtc_program_ss(rdev, ATOM_DISABLE, ATOM_DCPLL, -1, &ss);
>                 /* XXX: DCE5, make sure voltage, dispclk is high enough */
>                 atombios_crtc_set_disp_eng_pll(rdev, rdev->clock.default_dispclk);
>                 if (ss_enabled)
> -                       atombios_crtc_program_ss(rdev, ATOM_ENABLE, ATOM_DCPLL, &ss);
> +                       atombios_crtc_program_ss(rdev, ATOM_ENABLE, ATOM_DCPLL, -1, &ss);
>         }
>
>  }
> --
> 1.7.1
>
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