Re: [Intel-gfx] [PATCH 2/6] drm/i915/bios: Use i915->vbt.ports[] on CHV

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Dec 22, 2021 at 11:05:50AM +0200, Jani Nikula wrote:
> On Fri, 17 Dec 2021, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >
> > CHV is currently straddling the divide by using parse_ddi_ports() stuff
> > for aux_ch/ddc_pin but going through all old codepaths for the rest
> > (intel_bios_is_port_present(), intel_bios_is_port_edp(),
> > intel_bios_is_port_dp_dual_mode()). Let's switch over full and use
> > i915->vbt.ports[] for the rest of the stuff.
> 
> Whoa, this is far more subtle than what the code looks!
> 
> We stop checking for port A for CHV in intel_bios_is_port_present(), but
> it's a warn and I don't recall any bug reports, so probably fine. We
> could add a check in parse_ddi_port(), but meh.
> 
> Ditto for intel_bios_is_port_dp_dual_mode(), except it doesn't have a
> warn.
> 
> The eDP check in intel_bios_is_port_edp() becomes slightly more
> relaxed. Both the old and new check require these to be set:
> 
>  - DEVICE_TYPE_DISPLAYPORT_OUTPUT
>  - DEVICE_TYPE_INTERNAL_CONNECTOR.
> 
> The old code also required these to be unset:
> 
>  - DEVICE_TYPE_MIPI_OUTPUT
>  - DEVICE_TYPE_COMPOSITE_OUTPUT
>  - DEVICE_TYPE_DUAL_CHANNEL
>  - DEVICE_TYPE_LVDS_SIGNALING
>  - DEVICE_TYPE_TMDS_DVI_SIGNALING
>  - DEVICE_TYPE_VIDEO_SIGNALING
>  - DEVICE_TYPE_ANALOG_OUTPUT
> 
> It's possible we've added these just as a sanity check for broken VBTs
> more than anything. I guess I'd see if actual problems arise.
> 
> Bottom line, I think the functional changes matter only for VBTs with
> bogus data.

Yeah, I should probably include a bit more of thse details in this
commit message as well to make it easier to figure out what actually
changed if we get a regressoion.

> Reviewed-by: Jani Nikula <jani.nikula@intel.com>

Thanks.

-- 
Ville Syrjälä
Intel