On 26-05-21, 09:00, Jeffrey Hugo wrote:

On Tue, May 25, 2021 at 11:46 PM Vinod Koul [off-list ref] wrote:

quoted

On 21-05-21, 08:09, Jeffrey Hugo wrote:

quoted

On Fri, May 21, 2021 at 6:50 AM Vinod Koul [off-list ref] wrote:

quoted

Display Stream Compression (DSC) compresses the display stream in host which
is later decoded by panel. This series enables this for Qualcomm msm driver.
This was tested on Google Pixel3 phone which use LGE SW43408 panel.

The changes include adding DT properties for DSC then hardware blocks support
required in DPU1 driver and support in encoder. We also add support in DSI
and introduce required topology changes.

In order for panel to set the DSC parameters we add dsc in drm_panel and set
it from the msm driver.

Complete changes which enable this for Pixel3 along with panel driver (not
part of this series) and DT changes can be found at:
git.linaro.org/people/vinod.koul/kernel.git pixel/dsc_rfc

Comments welcome!

This feels backwards to me.  I've only skimmed this series, and the DT
changes didn't come through for me, so perhaps I have an incomplete
view.

Not sure why, I see it on lore:
https://lore.kernel.org/dri-devel/20210521124946.3617862-3-vkoul@kernel.org/ (local)

quoted

DSC is not MSM specific.  There is a standard for it.  Yet it looks
like everything is implemented in a MSM specific way, and then pushed
to the panel.  So, every vendor needs to implement their vendor
specific way to get the DSC info, and then push it to the panel?
Seems wrong, given there is an actual standard for this feature.

I have added slice and bpp info in the DT here under the host and then
pass the generic struct drm_dsc_config to panel which allows panel to
write the pps cmd

Nothing above is MSM specific.. It can very well work with non MSM
controllers too.

I disagree.

The DT bindings you defined (thanks for the direct link) are MSM
specific.  I'm not talking (yet) about the properties you defined, but
purely from the stand point that you defined the binding within the
scope of the MSM dsi binding.  No other vendor can use those bindings.
Of course, if we look at the properties themselves, they are prefixed
with "qcom", which is vendor specific.

So, purely on the face of it, this is MSM specific.

Assuming we want a DT solution for DSC, I think it should be something
like Documentation/devicetree/bindings/clock/clock-bindings.txt (the
first example that comes to mind), which is a non-vendor specific
generic set of properties that each vendor/device specific binding can
inherit.  Panel has similar things.

Specific to the properties, I don't much like that you duplicate BPP,
which is already associated with the panel (although perhaps not in
the scope of DT).  What if the panel and your DSC bindings disagree?
Also, I guess I need to ask, have you read the DSC spec?  Last I
looked, there were something like 3 dozen properties that could be
configured.  You have five in your proposed binding.  To me, this is
not a generic DSC solution, this is MSM specific (and frankly I don't
think this supports all the configuration the MSM hardware can do,
either).

I would concede the point that DT is msm specific. I dont disagree on
making them a common dsc biding which anyone can use. I think your idea
does have merits...

I am still not sure who should include these properties, would it be the
panel or host. Either would work and rest of the system can use these
properties...

-- 
~Vinod