linux-kernel - Re: [PATCH v7 05/12] clocksource: mips-gic-timer: Always use cluster 0 counter as clocksource

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Message-ID: <241d5547-eefb-4616-990a-7da8d8fa4fbc@linaro.org>
Date: Mon, 28 Oct 2024 17:09:50 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Aleksandar Rikalo <arikalo@...il.com>,
 Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: Chao-ying Fu <cfu@...ecomp.com>, Geert Uytterhoeven
 <geert@...ux-m68k.org>, Greg Ungerer <gerg@...nel.org>,
 Hauke Mehrtens <hauke@...ke-m.de>,
 Ilya Lipnitskiy <ilya.lipnitskiy@...il.com>,
 Jiaxun Yang <jiaxun.yang@...goat.com>, linux-kernel@...r.kernel.org,
 linux-mips@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
 Paul Burton <paulburton@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
 Serge Semin <fancer.lancer@...il.com>, Thomas Gleixner <tglx@...utronix.de>,
 Tiezhu Yang <yangtiezhu@...ngson.cn>,
 Gregory CLEMENT <gregory.clement@...tlin.com>
Subject: Re: [PATCH v7 05/12] clocksource: mips-gic-timer: Always use cluster
 0 counter as clocksource

On 19/10/2024 09:10, Aleksandar Rikalo wrote:
> From: Paul Burton <paulburton@...nel.org>
> 
> In a multi-cluster MIPS system, there are multiple GICs - one in each
> cluster - each of which has its independent counter. The counters in
> each GIC are not synchronized in any way, so they can drift relative
> to one another through the lifetime of the system. This is problematic
> for a clock source which ought to be global.
> 
> Avoid problems by always accessing cluster 0's counter, using
> cross-cluster register access. This adds overhead so it is applied only
> on multi-cluster systems.
> 
> Signed-off-by: Paul Burton <paulburton@...nel.org>
> Signed-off-by: Chao-ying Fu <cfu@...ecomp.com>
> Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@...mia.com>
> Signed-off-by: Aleksandar Rikalo <arikalo@...il.com>
> Tested-by: Serge Semin <fancer.lancer@...il.com>
> ---


Applied, thanks


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