linux-kernel - Re: [PATCH v2 05/16] dt-bindings: display/msm: dp-controller: Add SM8750

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Message-ID: <CAA8EJpoWEuqKkreUTu1gO-Pr=VFNNP_vBfNZpitJiJH728vjPA@mail.gmail.com>
Date: Tue, 25 Feb 2025 05:14:36 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Rob Clark <robdclark@...il.com>, 
	Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Krishna Manikandan <quic_mkrishn@...cinc.com>, Jonathan Marek <jonathan@...ek.ca>, 
	Kuogee Hsieh <quic_khsieh@...cinc.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Srini Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH v2 05/16] dt-bindings: display/msm: dp-controller: Add SM8750

On Mon, 24 Feb 2025 at 20:59, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>
>
>
> On 2/19/2025 9:08 AM, Dmitry Baryshkov wrote:
> > On Wed, Feb 19, 2025 at 06:02:20PM +0100, Krzysztof Kozlowski wrote:
> >> On 17/02/2025 19:58, Dmitry Baryshkov wrote:
> >>> On Mon, Feb 17, 2025 at 05:41:26PM +0100, Krzysztof Kozlowski wrote:
> >>>> Add DisplayPort controller for Qualcomm SM8750 SoC which so far looks
> >>>> fully compatible with earlier SM8650 variant.
> >>>
> >>> As that became a question for QCS8300, does SM8750 also support exactly
> >>> two MST streams?
> >>
> >> v1.5 of DP (starting from SA8775p , then SM8650 and SM8750) support 4x
> >> MST for DPTX0 and 2x MST for DPTX1.
> >>
> >> The DP in SM8650 and SM8750 are identical, according to datasheet (v1.5.1).
> >
> > Hmm. This also means that QCS8300 is compatible with SM8650. I'll let
> > Abhinav comment here.
> >
>
> DP version by itself is not a good measure of whether the controller can
> support 4 streams or not.
>
> Firstly, sm8650/sm8750 do not have a DPTX1 so we are only discussing
> about DP TX0.
>
> Coming to the QCS8300 Vs sm8650/sm8750, even though the DP controller
> version is the same, there is no HW support for more than 2 streams on
> sm8650/sm8750 because there are no INTF blocks to drive 4 streams.
>
> On sm8650/sm8750, only INTF_0 and INTF_3 can be used for DP. Hence 2
> streams.
>
> Whereas on Monaco, we have INTF_0, INTF_3, INTF_6 and INTF_7 capable of

No idea what Monaco is, most likely it is some platform. Please use
SoC names in public.

> driving DP. Hence 4 streams.
>
> Let me know if there are more questions.

How many stream clocks are present on those platforms? I'm asking
because there is a small, but not non-existing difference between 'DPs
are not completely compatible / the same' and 'DPs are fully
compatible but different DPU blocks impose different restrictions on
the number of MST streams'.

-- 
With best wishes
Dmitry