linux-kernel - Re: [PATCH v4 07/14] clocksource: mips-gic-timer: Always use cluster 0 counter as clocksource

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Message-ID: <Zoz6kvcio/wl/015@alpha.franken.de>
Date: Tue, 9 Jul 2024 10:53:38 +0200
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>,
	Aleksandar Rikalo <aleksandar.rikalo@...mia.com>,
	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>,
	linux-kernel@...r.kernel.org,
	"linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>,
	Marc Zyngier <maz@...nel.org>,
	"paulburton@...nel.org" <paulburton@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Serge Semin <fancer.lancer@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH v4 07/14] clocksource: mips-gic-timer: Always use cluster
 0 counter as clocksource

On Tue, Jul 09, 2024 at 09:47:52AM +0800, Jiaxun Yang wrote:
> 
> 
> 在2024年7月9日七月 上午12:36，Daniel Lezcano写道：
> > On 11/05/2024 12:43, Aleksandar Rikalo wrote:
> >> From: Paul Burton <paulburton@...nel.org>
> >> 
> >> In a multi-cluster MIPS system we have multiple GICs - one in each
> >> cluster - each of which has its own independent counter. The counters in
> >> each GIC are not synchronised in any way, so they can drift relative to
> >> one another through the lifetime of the system. This is problematic for
> >> a clocksource which ought to be global.
> >> 
> >> Avoid problems by always accessing cluster 0's counter, using
> >> cross-cluster register access. This adds overhead so we only do so on
> >> systems where we actually have CPUs present in multiple clusters.
> >> For now, be extra conservative and don't use gic counter for vdso or
> >> sched_clock in this case.
> >> 
> >> 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 <aleksandar.rikalo@...mia.com>
> >> ---
> >
> > Applied patch 7 and 8
> 
> I think it won't compile without patch 1 being applid.
> 
> Thomas, do you mind to apply patch 1 for now? Given that it's just some extra
> function definitions.

no problem, I've applied patch 1 und 2 to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]