linux-kernel - Re: [PATCH v3 12/17] clk: mediatek: mt8365-mm: fix DPI0 parent

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Date: Fri, 19 Apr 2024 09:34:49 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Alexandre Mergnat <amergnat@...libre.com>,
 Chun-Kuang Hu <chunkuang.hu@...nel.org>,
 Philipp Zabel <p.zabel@...gutronix.de>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Matthias Brugger
 <matthias.bgg@...il.com>, Jitao Shi <jitao.shi@...iatek.com>,
 CK Hu <ck.hu@...iatek.com>, Uwe Kleine-König
 <u.kleine-koenig@...gutronix.de>, Michael Turquette
 <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>,
 Fabien Parent <fparent@...libre.com>,
 Markus Schneider-Pargmann <msp@...libre.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-pwm@...r.kernel.org,
 linux-clk@...r.kernel.org
Subject: Re: [PATCH v3 12/17] clk: mediatek: mt8365-mm: fix DPI0 parent

Il 18/04/24 16:17, Alexandre Mergnat ha scritto:
> To have a working display through DPI, a workaround has been
> implemented downstream to add "mm_dpi0_dpi0" and "dpi0_sel" to
> the DPI node. Shortly, that add an extra clock.
> 
> It seems consistent to have the "dpi0_sel" as parent.
> Additionnaly, "vpll_dpix" isn't used/managed.
> 
> Then, set the "mm_dpi0_dpi0" parent clock to "dpi0_sel".
> 
> The new clock tree is:
> 
> clk26m
>    lvdspll
>      lvdspll_X (2, 4, 8, 16)
>        dpi0_sel
>          mm_dpi0_dpi0
> 
> Fixes: d46adccb7966 ("clk: mediatek: add driver for MT8365 SoC")
> Signed-off-by: Alexandre Mergnat <amergnat@...libre.com>

I wonder what CLK_TOP_VPLL_DPIX_EN is for, but since you've ruled it out
by removing the dependency, this clock is 100% being disabled because unused
and the DPI interface clearly still works.

I also wonder if that clock is getting en/disabled by HW control mechanism...
..because that'd make sense, as this is .. well, a DPI clock.

That's just out of curiosity though, as I'd really like to understand whenwhatwhy
for stuff....

In any case, whether you have an answer or not, this commit is:

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

Cheers!