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

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Date:   Wed, 17 May 2023 11:34:32 +0200
From:   Alexandre Mergnat <amergnat@...libre.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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 10:40, Krzysztof Kozlowski wrote:
> 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.

I will.

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

Briefly, clocks with the higher index than the data clock array can't be 
used. I've this issue:
[    0.427054] of_clk_hw_onecell_get: invalid index 135
[    0.429525] of_clk_hw_onecell_get: invalid index 69
[    0.442998] of_clk_hw_onecell_get: invalid index 70

That means CLK_TOP_SSUSB_PHY_CK_EN, CLK_IFR_SSUSB_REF and 
CLK_IFR_SSUSB_XHCI aren't working when I need them. So my USB doesn't work.

> 
>>
>> 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?!?

I've under-estimated the impact of modifying the defines, I will try to 
find another way to fix the regression in the drivers directly.

Thanks for your review.

> 
> Best regards,
> Krzysztof
> 
> 

-- 
Regards,
Alexandre