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

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Message-ID: <Zx+yEvWTUKZqOEPh@alpha.franken.de>
Date: Mon, 28 Oct 2024 16:47:30 +0100
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Aleksandar Rikalo <arikalo@...il.com>, 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 Mon, Oct 28, 2024 at 04:22:55PM +0100, Daniel Lezcano wrote:
> On 28/10/2024 16:15, Thomas Bogendoerfer wrote:
> > On Mon, Oct 28, 2024 at 03:54:48PM +0100, Daniel Lezcano wrote:
> > > 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>
> > > > ---
> > > 
> > > May I take this patch through the clocksource tree ?
> > 
> > sure, should be the best option.
> 
> Ok, thanks
> 
> Can you add your tag ?

it's only touching drivers/clocksource, but if you want

Acked-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>

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