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SubjectRe: [Intel-gfx] [PATCH 5/7] drm/i915: Make DP prepare/commit consistent with DP dpms
On Thu, 03 Nov 2011 15:30:57 -0700
Keith Packard <keithp@keithp.com> wrote:

> On Thu, 3 Nov 2011 13:00:11 -0700, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
>
> > A few comments on this one (also, is it strictly required to fix your
> > bug)?
>
> I think so; the panel definitely was not happy when I turned the link
> off while the panel power was on. Having the mode setting and DPMS paths
> doing things in different orders definitely doesn't seem reasonable
> though. I nearly managed to share code between the two paths, but there
> are subtle differences in requirements and so I didn't bother.
>
> > Ok so you're making sure the panel has power to down the link, I think
> > that's fine.
>
> No, I'm turning the panel off *before* turning off the link. The panel
> goes nuts if you down the link before turning its power off; lots of
> technicolor.

Except for VDD?? That does come on... and shouldn't be any different
than a full power sequence as far as link training etc go...

> Downing the link doesn't require any communication with the panel, so
> there's no issue with losing connectivity at this point:
>
> ironlake_edp_backlight_off(intel_dp);
> ironlake_edp_panel_off(intel_dp); <= panel off
>
> /* Wake up the sink first */
> ironlake_edp_panel_vdd_on(intel_dp);
> intel_dp_sink_dpms(intel_dp, DRM_MODE_DPMS_ON);
> intel_dp_link_down(intel_dp); <= link down
> ironlake_edp_panel_vdd_off(intel_dp, false);
>
> > But here it looks like you're shutting it off, then downing the link?
> > Should this be reordered?
>
> Nope, it's in the same order:
>
> ironlake_edp_backlight_off(intel_dp);
> ironlake_edp_panel_off(intel_dp); <= panel off
>
> ironlake_edp_panel_vdd_on(intel_dp);
> intel_dp_sink_dpms(intel_dp, mode);
> intel_dp_link_down(intel_dp); <= link down
> ironlake_edp_panel_vdd_off(intel_dp, false);
>
> The only difference in these two code paths is that dp_prepare turns the
> sink to DPMS_ON, while dp_dpms turns the sink to DPMS_OFF.

Oh missed the vdd on, which is in this path too... So I'm still
confused by the panel off, vdd on sequence, but at least they're
consistent.

--
Jesse Barnes, Intel Open Source Technology Center
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