[Intel-gfx] [PATCH v4] drm/i915: Try to guess PCH type even without ISA bridge

[Joonas Lahtinen]

Quoting Jani Nikula (2021-01-15 12:50:54)
> On Thu, 14 Jan 2021, Zhenyu Wang <zhenyuw at linux.intel.com> wrote:
> > On 2021.01.14 08:58:19 +0800, Xiong Zhang wrote:
> >> From: Zhenyu Wang <zhenyuw at linux.intel.com>
> >> 
> >> Some vmm like hyperv and crosvm don't supply any ISA bridge to their guest,
> >> when igd passthrough is equipped on these vmm, guest i915 display may
> >> couldn't work as guest i915 detects PCH_NONE pch type.
> >> 
> >> When i915 runs as guest, this patch guess pch type through gpu type even
> >> without ISA bridge.
> >> 
> >> v2: Fix CI warning
> >> v3: Add HAS_DISPLAY()= true condition beforce guessing virt pch, then
> >>     refactori.
> >> v4: Fix CI warning
> >> 
> >> Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> >> Signed-off-by: Xiong Zhang <xiong.y.zhang at intel.com>
> >> ---
> >>  drivers/gpu/drm/i915/i915_drv.h  |  7 +++++-
> >>  drivers/gpu/drm/i915/intel_pch.c | 39 ++++++++++++++++++--------------
> >>  2 files changed, 28 insertions(+), 18 deletions(-)
> >>
> >
> > Good to me, thanks! I think this should change author to you. :)
> >
> > Reviewed-by: Zhenyu Wang <zhenyuw at linux.intel.com>
> 
> Pushed to drm-intel-next, thanks for the patch and review. I ended up
> retaining Zhenyu's authorship, and added
> 
> Co-developed-by: Xiong Zhang <xiong.y.zhang at intel.com>

This only works for the majority of SKUs which happen to use the PCH
that is most common. I NAKed very similar patch some years back asking
for a reliable means to detect the PCH type instead.

Has there been any attempt to introduce such mechanism?

Regards, Joonas