linux-kernel - Re: [v1] dt-bindings: msm:disp: update dsi and dpu bindings

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Date:   Tue, 4 Feb 2020 10:22:09 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Harigovindan P <harigovi@...eaurora.org>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        "Kristian H. Kristensen" <hoegsberg@...omium.org>,
        Kalyan Thota <kalyan_t@...eaurora.org>, nganji@...eaurora.org
Subject: Re: [v1] dt-bindings: msm:disp: update dsi and dpu bindings

Hi,

On Tue, Feb 4, 2020 at 6:15 AM Harigovindan P <harigovi@...eaurora.org> wrote:
>
> Updating bindings of dsi and dpu by adding and removing certain
> properties.
>
> Signed-off-by: Harigovindan P <harigovi@...eaurora.org>
> ---
>
> Changes in v1:
>         - Adding "ahb" clock as a required property.
>         - Adding "bus", "rot", "lut" as optional properties for sc7180 device.
>         - Removing properties from dsi bindings that are unused.
>         - Removing power-domain property since DSI is the child node of MDSS
>           and it will inherit supply from its parent.
>
>  Documentation/devicetree/bindings/display/msm/dpu.txt | 7 +++++++
>  Documentation/devicetree/bindings/display/msm/dsi.txt | 5 -----
>  2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/display/msm/dpu.txt b/Documentation/devicetree/bindings/display/msm/dpu.txt
> index 551ae26..dd58472a 100644
> --- a/Documentation/devicetree/bindings/display/msm/dpu.txt
> +++ b/Documentation/devicetree/bindings/display/msm/dpu.txt
> @@ -19,6 +19,7 @@ Required properties:
>    The following clocks are required:
>    * "iface"
>    * "bus"
> +  * "ahb"

This is only required for sc7180?  ...or old SoCs should have had it
all along too?


>    * "core"
>  - interrupts: interrupt signal from MDSS.
>  - interrupt-controller: identifies the node as an interrupt controller.
> @@ -50,6 +51,8 @@ Required properties:
>  - clock-names: device clock names, must be in same order as clocks property.
>    The following clocks are required.
>    * "bus"
> +  For the device "qcom,sc7180-dpu":
> +  * "bus" - is an optional property due to architecture change.

This is a really odd way to write it for two reasons:
* You're breaking up the flow of the list.
* This shouldn't be listed as "optional" in sc7180 but unless there is
some reason to ever provide it on sc7180.  It should simply be
disallowed.

Maybe instead just:

   The following clocks are required.
-  * "bus"
+  * "bus" (anything other than qcom,sc7180-dpu)

We really need to get this into yaml ASAP but that'd probably be OK to
tide us over.

NOTE: when converting to yaml, ideally we'll have a separate file per
SoC to avoid crazy spaghetti, see commit 2a8aa18c1131 ("dt-bindings:
clk: qcom: Fix self-validation, split, and clean cruft") in clk-next
for an example of starting the transition to one yaml per SoC (at
least for anything majorly different).


>    * "iface"
>    * "core"
>    * "vsync"
> @@ -70,6 +73,10 @@ Optional properties:
>  - assigned-clocks: list of clock specifiers for clocks needing rate assignment
>  - assigned-clock-rates: list of clock frequencies sorted in the same order as
>    the assigned-clocks property.
> +- For the device "qcom,sc7180-dpu":
> +  clock-names: optional device clocks, needed for accessing LUT blocks.
> +  * "rot"
> +  * "lut"
>
>  Example:
>
> diff --git a/Documentation/devicetree/bindings/display/msm/dsi.txt b/Documentation/devicetree/bindings/display/msm/dsi.txt
> index af95586..61d659a 100644
> --- a/Documentation/devicetree/bindings/display/msm/dsi.txt
> +++ b/Documentation/devicetree/bindings/display/msm/dsi.txt
> @@ -8,13 +8,10 @@ Required properties:
>  - reg-names: The names of register regions. The following regions are required:
>    * "dsi_ctrl"
>  - interrupts: The interrupt signal from the DSI block.
> -- power-domains: Should be <&mmcc MDSS_GDSC>.

Is this supposed to be removed from all SoCs using this bindings, or
just yours?

I'll also note that you left it in the "Example:" below.


>  - clocks: Phandles to device clocks.
>  - clock-names: the following clocks are required:
> -  * "mdp_core"
>    * "iface"
>    * "bus"
> -  * "core_mmss"

As Jeffrey pointed out, you shouldn't be removing these from old SoCs.
In "drivers/gpu/drm/msm/dsi/dsi_cfg.c" you can clearly see them used.
Maybe it's time for you to do the yaml conversion and handle this
correctly per-SoC.

-Doug