Re: [Intel-gfx] [PATCH v2] drm/i915/edp/jsl: Update vswing table for HBR and HBR2

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 30 Sep 2020, Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> Now we have an actual difference between EHL and JSL so we
> should split. Granted it's a bit annoying to have to do it
> just for some vswing tables. Ideally that stuff would be
> specified in a sane way by the VBT. But since VBT is generally
> useless we need to deal with this on a platform level.

Just to recap, we have three basic approaches for differentiating
platforms based on PCI ID:

- Separate platforms, each with their own device info and enum
  intel_platform, using IS_<PLATFORM>() for checks.

- Same platform, with subplatforms, using IS_SUBPLATFORM() for
  checks. Generally only used for the ULT/ULX checks, but there's also
  the CNL/ICL port F case which is perhaps comparable.

- Same platform, each with their own device info, and a feature flag.

(In this case, checking the PCH is a proxy; there is no actual
difference in the PCHs to account for the different values to be
used. Mixing PCHs with the platforms would lead to problems.)

We've been told JSL and EHL are the same, which would argue for keeping
them INTEL_ELKHARTLAKE. We've done this with other platforms that are
identical. However, now it looks like they're not the same... why not if
they're supposed to be identical? What else is there?

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center
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