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From: Jim Quinlan <james.quinlan@broadcom.com>
To: Lukasz Luba <lukasz.luba@arm.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: Fri, 20 Dec 2019 11:24:03 -0500	[thread overview]
Message-ID: <9befbc13-ba00-094d-0064-0d97c1ccbb63@broadcom.com> (raw)
In-Reply-To: <7fe599d3-1ce2-1fde-2911-9516a26090b6@arm.com>


> 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!

Regards,
Jim Quinlan


  reply	other threads:[~2019-12-20 16:24 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 [this message]
2019-12-23 15:39           ` Lukasz Luba

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