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

From: Alexandre Mergnat <amergnat@baylibre.com>
To: Conor Dooley <conor@kernel.org>
Cc: Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>, Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	Chen-Yu Tsai <wenst@chromium.org>,
	Markus Schneider-Pargmann <msp@baylibre.com>,
	linux-clk@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH v2 1/2] dt-bindings: clock: mediatek: replace unusable clock
Date: Fri, 26 May 2023 10:54:04 +0200	[thread overview]
Message-ID: <c1e706f3-9d80-3dd5-eeab-c24830f9ef03@baylibre.com> (raw)
In-Reply-To: <20230525-snuggle-twine-ed1bfc2aee51@spud>

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

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