linux-kernel - Re: [PATCH v2 1/2] dt-bindings: clock: mediatek: replace unusable clock

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Date:   Fri, 26 May 2023 10:54:04 +0200
From:   Alexandre Mergnat <amergnat@...libre.com>
To:     Conor Dooley <conor@...nel.org>
Cc:     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>,
        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 v2 1/2] dt-bindings: clock: mediatek: replace unusable
 clock

On 25/05/2023 19:51, Conor Dooley wrote:
> On Thu, May 25, 2023 at 04:50:27PM +0200, Alexandre Mergnat wrote:
>> The “mcu_pm_bclk_ck_cg” clock is used by co-processors and should not be
>> added to the kernel driver, otherwise the CPU just halt and the board is
>> rebooted by the wathdog.
>>
>> Instead, add the "aes_top0_bclk_ck_cg" missing clock to prevent
>> re-shuffling index and then preserve the ABI.
> 
> How does this preserve the ABI exactly? Please describe exactly what you
> mean by that.

I mean that reduce the impact of the change compared to the v1 where 
I've changed the index of the following defines to be clean.

> Also, what about any other users of these definitions, outside of Linux?

The clock driver and bindings are only a couple of kernel versions old, 
I'm pretty sure no one is using it. Also, if someone use 
CLK_IFR_MCU_PM_BK define, I'm wondering how his CPU is working since 
Mediatek told me that shouldn't be used, and after some try, I confirm.

I've a question: If something is wrong in the binding, you don't fix it 
to avoid ABI change ?

TBH, I just try to clean the binding. I can fix the driver index issue 
(patch 2/2) without fixing the binding if you prefer. But IMHO, keep an 
unusable define isn't great...

-- 
Regards,
Alexandre