linux-kernel - Re: [PATCH 1/2] clk: mediatek: mt8365: fix the clock indexes

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Date:   Wed, 17 May 2023 10:40:11 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Alexandre Mergnat <amergnat@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Chen-Yu Tsai <wenst@...omium.org>
Cc:     Markus Schneider-Pargmann <msp@...libre.com>,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 1/2] clk: mediatek: mt8365: fix the clock indexes

On 17/05/2023 10:28, Alexandre Mergnat wrote:
> Before the patch [1], the clock probe was done directly in the
> clk-mt8365 driver. In this probe function, the array which stores the
> data clocks is sized using the higher defined numbers (*_NR_CLOCK) in
> the clock lists [2]. Currently, with the patch [1], the specific
> clk-mt8365 probe function is replaced by the mtk generic one [3], which
> size the clock data array by adding all the clock descriptor array size
> provided by the clk-mt8365 driver.
> 
> Actually, all clock indexes come from the header file [2], that mean, if
> there are more clock (then more index) in the header file [2] than the
> number of clock declared in the clock descriptor arrays (which is the
> case currently), the clock data array will be undersized and then the
> generic probe function will overflow when it will try to write in
> "clk_data[CLK_INDEX]". Actually, instead of crashing at boot, the probe
> function returns an error in the log which looks like:
> "of_clk_hw_onecell_get: invalid index 135", then this clock isn't
> enabled.

Please use subject prefixes matching the subsystem. You can get them for
example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
your patch is touching.

This is huge ABI break and I don't understand why it is needed. Entire
description above did not explain me that.

> 
> The simplest way to fix the regression is to remove from the header file
> [2] the unused clocks.

??? The simples is to revert the patch, so you won't break the ABI.

> 
> [1]: Commit ffe91cb28f6a ("clk: mediatek: mt8365: Convert to
>      mtk_clk_simple_{probe,remove}()")
> [2]: include/dt-bindings/clock/mediatek,mt8365-clk.h
> [3]: drivers/clk/mediatek/clk-mtk.c
> 
> Fixes: ffe91cb28f6a ("clk: mediatek: mt8365: Convert to mtk_clk_simple_{probe,remove}()")
> 
> Signed-off-by: Alexandre Mergnat <amergnat@...libre.com>
> ---
>  include/dt-bindings/clock/mediatek,mt8365-clk.h | 361 ++++++++++++------------
>  1 file changed, 177 insertions(+), 184 deletions(-)
> 
> diff --git a/include/dt-bindings/clock/mediatek,mt8365-clk.h b/include/dt-bindings/clock/mediatek,mt8365-clk.h
> index f9aff1775810..fd59c8bdeb24 100644
> --- a/include/dt-bindings/clock/mediatek,mt8365-clk.h
> +++ b/include/dt-bindings/clock/mediatek,mt8365-clk.h
> @@ -7,147 +7,142 @@
>  #define _DT_BINDINGS_CLK_MT8365_H
>  
>  /* TOPCKGEN */
> -#define CLK_TOP_CLK_NULL		0> -#define CLK_TOP_I2S0_BCK		1

...

> +#define CLK_TOP_I2S0_BCK		0

Why? This is really broken. You can remove the defines, but re-shuffling
everything?!?

Best regards,
Krzysztof