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

[abhinavk]

On 2021-06-02 04:01, Vinod Koul wrote:
> On 27-05-21, 16:30, Rob Clark wrote:
> > On Wed, May 26, 2021 at 8:00 AM Jeffrey Hugo 
> > <jeffrey.l.hugo@xxxxxxxxx> wrote:
> > > On Tue, May 25, 2021 at 11:46 PM Vinod Koul <vkoul@xxxxxxxxxx> 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..?

At the moment, I will comment on the bindings first and my idea on how 
to proceed.
The bindings mentioned here: 
https://lore.kernel.org/dri-devel/20210521124946.3617862-3-vkoul@xxxxxxxxxx/ 
seem to be just
taken directly from downstream which was not the plan.

I think all of these should be part of the generic panel bindings as 
none of these are QC specific:

@@ -188,6 +195,14 @@ Example:
 		qcom,master-dsi;
 		qcom,sync-dual-dsi;

+		qcom,mdss-dsc-enabled;
+		qcom,mdss-slice-height = <16>;
+		qcom,mdss-slice-width = <540>;
+		qcom,mdss-slice-per-pkt = <1>;
+		qcom,mdss-bit-per-component = <8>;
+		qcom,mdss-bit-per-pixel = <8>;
+		qcom,mdss-block-prediction-enable;
+

How about having a panel-dsc.yaml which will have these properties and 
have a panel-dsc node to have this information?

I would like to hear the feedback on this proposal then the series can 
be reworked.

Thanks

Abhinav