linux-kernel - Re: [PATCH v3 0/9] coresight: change some driver' spinlock type to raw_spinlock

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Message-ID: <ac537889-dc0a-4d2e-870b-c5a33279633e@arm.com>
Date: Fri, 20 Dec 2024 11:35:36 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Yeoreum Yun <yeoreum.yun@....com>, Mike Leach <mike.leach@...aro.org>
Cc: james.clark@...aro.org, alexander.shishkin@...ux.intel.com,
 bigeasy@...utronix.de, clrkwllms@...nel.org, rostedt@...dmis.org,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev
Subject: Re: [PATCH v3 0/9] coresight: change some driver' spinlock type to
 raw_spinlock_t

On 20/12/2024 10:38, Yeoreum Yun wrote:
> Hi Mike.
> 
>> Notably missing is the same changes for the etm3x driver. The ETMv3.x
>> and PTM1.x are supported by this driver, and these trace source
>> variants are also supported in perf in the cs_etm.c code.
> 
> But I wonder etmv3 needs to change. Because its spinlock is used only
> via sysfs enable/disable path.
> So, I think it doesn't need to change the lock type.

ETM3 can be used in perf mode, similar to the ETM4x.

So, you need to fix it as well.


> 
>> STM is also missing, though this is not directly enabled via perf -
>> but could perhaps run concurrently as it can be a target output for
>> ftrace.
> 
> Actually, I couldn't find out the path where
> the STM's lock could be grabbed under other raw_spin_lock (including csdev)
> If you don't mind would you let me the code path please?

STM can't be used in perf mode, and as such you may skip it.

Suzuki


> 
> Thanks
>> --
>> Mike Leach
>> Principal Engineer, ARM Ltd.
>> Manchester Design Centre. UK