linux-kernel - Re: [Freedreno] [RFC PATCH 00/13] drm/msm: Add Display Stream Compression Support

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Message-ID: <YLdlEB3Ea6OWaLw4@vkoul-mobl>
Date:   Wed, 2 Jun 2021 16:31:36 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
        DTML <devicetree@...r.kernel.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        David Airlie <airlied@...ux.ie>,
        MSM <linux-arm-msm@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        freedreno <freedreno@...ts.freedesktop.org>
Subject: Re: [Freedreno] [RFC PATCH 00/13] drm/msm: Add Display Stream
 Compression Support

On 27-05-21, 16:30, Rob Clark wrote:
> On Wed, May 26, 2021 at 8:00 AM Jeffrey Hugo <jeffrey.l.hugo@...il.com> wrote:
> > On Tue, May 25, 2021 at 11:46 PM Vinod Koul <vkoul@...nel.org> wrote:

> > Frankly, I don't like the MSM ACPI solution that I've seen on the laptops.
> > The ACPI assumes the entire MDSS (including DSI parts) and GPU is one
> > device, and ultimately handled by one driver.  That driver needs to
> > get a value from UEFI (set by the bootloader) that is the "panel id".
> > Then the driver calls into ACPI (I think its _ROM, but I might be
> > mistaken, doing this from memory) with that id.  It gets back a binary
> > blob which is mostly an xml file (format is publicly documented) that
> > contains the panel timings and such.
> 
> tbh, I kinda suspect that having a single "gpu" device (which also
> includes venus, in addition to display, IIRC) in the ACPI tables is a
> windowsism, trying to make things look to userspace like a single "GPU
> card" in the x86 world.. but either way, I think the ACPI tables on
> the windows arm laptops which use dsi->bridge->edp is too much of a
> lost cause to even consider here.  Possibly ACPI boot on these devices
> would be more feasible on newer devices which have direct eDP out of
> the SoC without requiring external bridge/panel glue.

yeah that is always a very different world. although it might make sense
to use information in tables and try to deduce information about the
system can be helpful...

> I'd worry more about what makes sense in a DT world, when it comes to
> DT bindings.

And do you have thoughts on that..?

-- 
~Vinod