linux-kernel - Re: [PATCH v2 4/4] arm64: dts: imx8mp: change AUDIO_AXI_CLK

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Message-ID: <36451a88-bfc6-4402-8e16-890d524a9368@gmail.com>
Date: Mon, 24 Feb 2025 16:42:02 +0200
From: Mihalcea Laurentiu <laurentiumihalcea111@...il.com>
To: Adam Ford <aford173@...il.com>
Cc: Abel Vesa <abelvesa@...nel.org>, Peng Fan <peng.fan@....com>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Shawn Guo <shawnguo@...nel.org>, Marek Vasut <marex@...x.de>,
 Stephen Boyd <sboyd@...nel.org>, Shengjiu Wang <shengjiu.wang@....com>,
 Pengutronix Kernel Team <kernel@...gutronix.de>, linux-clk@...r.kernel.org,
 imx@...ts.linux.dev, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Lucas Stach <l.stach@...gutronix.de>
Subject: Re: [PATCH v2 4/4] arm64: dts: imx8mp: change AUDIO_AXI_CLK_ROOT
 freq. to 800MHz

On 21.02.2025 21:37, Adam Ford wrote:
> On Fri, Feb 21, 2025 at 1:11 PM Laurentiu Mihalcea
> <laurentiumihalcea111@...il.com> wrote:
>> From: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
>>
>> AUDIO_AXI_CLK_ROOT can't run at currently requested 600MHz w/ its parent
>> SYS_PLL1 configured at 800MHz. Configure it to run at 800MHz as some
>> applications running on the DSP expect the core to run at this frequency
>> anyways. This change also affects the AUDIOMIX NoC.
> Unless I am missing something, the i.MX 8M Plus Applications Processor
> Datasheet (rev 2.1)  has a table of frequencies, and
> AUDIO_AXI_CLK_ROOT is shown to be 600MHz nominal and 800MHz for
> overdrive.  I agree that it's likely not running at 600MHz now, but
> 800MHz may be out of spec for people who are using the nominal voltage
> instead of the overdrive, since overdrive requires higher voltages
> than the nominal.
>
> adam

You're right, this would not work if someone was using

nominal voltage. Do you have an upstream board in mind/usecase which

works with nominal voltage instead of overdrive? As far as I understood from

Lucas's patch ([1]) there's no upstream board using nominal voltage?

CC-ing Lucas on this as his patch ([1]) is similar to this in that they're both

trying to use overdrive clock frequencies in the DTSI and I'd very much like

to have some sort of consistency in the DTSI if possible.

[1]: https://lore.kernel.org/imx/20250204182737.3361431-1-l.stach@pengutronix.de/