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From: Lukasz Luba <lukasz.luba@arm.com>
To: Jim Quinlan <james.quinlan@broadcom.com>,
	Sudeep Holla <sudeep.holla@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	rostedt@goodmis.org
Subject: Re: [PATCH 1/2] include: trace: Add SCMI header with trace events
Date: Mon, 23 Dec 2019 15:39:09 +0000	[thread overview]
Message-ID: <abad5f94-ce0d-99c9-bb9a-754c56849aee@arm.com> (raw)
In-Reply-To: <9befbc13-ba00-094d-0064-0d97c1ccbb63@broadcom.com>


On 12/20/19 4:24 PM, Jim Quinlan wrote:
> 
>> Thank you for sharing your experiments and thoughts. I have probably
>> similar setup for stressing the communication channel, but I do also
>> some wired things in the firmware. That's why I need to measure these
>> delays. I am happy that it is useful for you also.
>>
>> I don't know if your firmware supports 'fast channel', but please keep
>> in mind that it is not tracked in this 'transfer_id'.
>> This transfer_id in v2 version does not show the real transfers
>> to the firmware since there is another path called 'fast channel' or
>> 'fast_switch' in the CPUfreq. It is in drivers/firmware/arm_scmi/perf.c
>> and the atomic variable is not incremented in that path. Adding it also
>> there just for atomic_inc() probably would add delays in the fast_switch
>> and also brings little value.
>> For the normal channel, where we have spinlocks and other stuff, this
>> atomic_inc() could stay in my opinion.
>>
>> Regards,
>> Lukasz
> Hi Lukasz,
> 
> We currently do not use "fast channels" - although it is possible we might someday.
> I find the transfer_id useful per your v2 even if it doesn't cover FC.  Thanks for
> submitting and discussing this!

Thank you for cooperation.

Regards,
Lukasz

> 
> Regards,
> Jim Quinlan
> 

      reply	other threads:[~2019-12-23 15:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-16 16:16 [PATCH 1/2] include: trace: Add SCMI header with trace events lukasz.luba
2019-12-16 16:16 ` [PATCH 2/2] drivers: firmware: scmi: Extend SCMI transport layer by " lukasz.luba
2019-12-16 22:15 ` [PATCH 1/2] include: trace: Add SCMI header with " Jim Quinlan
2019-12-17 10:05 ` Lukasz Luba
2019-12-18 12:09 ` Sudeep Holla
2019-12-18 16:37   ` Jim Quinlan
2019-12-19 16:32     ` Jim Quinlan
2019-12-20  9:20       ` Lukasz Luba
2019-12-20 16:24         ` Jim Quinlan
2019-12-23 15:39           ` Lukasz Luba [this message]

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