linux-kernel - Re: [PATCH 2/8] arm64: dts: s32g274-rd2: Enable the STM timers

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Message-ID: <4b2bd0ab-cc4b-4afd-a46e-60ccc8d6f239@linaro.org>
Date: Fri, 1 Aug 2025 10:23:08 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Frank Li <Frank.li@....com>
Cc: mbrugger@...e.com, chester62515@...il.com,
 ghennadi.procopciuc@....nxp.com, shawnguo@...nel.org,
 s.hauer@...gutronix.de, s32@....com, kernel@...gutronix.de,
 festevam@...il.com, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, linux-arm-kernel@...ts.infradead.org,
 imx@...ts.linux.dev, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Ghennadi Procopciuc <ghennadi.procopciuc@....com>,
 Thomas Fossati <thomas.fossati@...aro.org>
Subject: Re: [PATCH 2/8] arm64: dts: s32g274-rd2: Enable the STM timers

On 01/08/2025 01:17, Frank Li wrote:
> On Wed, Jul 30, 2025 at 11:15:54PM +0200, Daniel Lezcano wrote:
>> On 30/07/2025 22:21, Frank Li wrote:
>>> On Wed, Jul 30, 2025 at 09:50:15PM +0200, Daniel Lezcano wrote:
>>>> Enable the timers STM0 -> STM3 on the s32g274-rd2
>>>>
>>>> The platform has 4 CPUs and the Linux STM timer driver is per
>>>> CPU. Enable 4 timers which will be used, other timers are useless for
>>>> the Linux kernel and there is no benefit to enable them.
>>>
>>> S32 have not ARM local timer? It is quite strange!
>>
>> I'm not saying there is no architected timers but there are the STM. May be
>> I can reword the sentence to prevent this ambiguity.
> 
> if there are local timer, why need STM for each core here?

Yes, I had initially the same question when upstreaming the STM timer. 
Ghennadi explained the automotive designs can partition the system by 
running a firmware and several instances of Linux. By using the STM, it 
is then possible to have the firmware to read the STM counters or to 
stop the timers when the board switches to debug mode.

Ghennadi can elaborate more on this if you need more context.


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