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([2a05:6e02:1041:c10:cf24:cce:17df:12ab]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-4266f6f5f51sm5021515e9.25.2024.07.08.09.36.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Jul 2024 09:36:08 -0700 (PDT) Message-ID: Date: Mon, 8 Jul 2024 18:36:07 +0200 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 07/14] clocksource: mips-gic-timer: Always use cluster 0 counter as clocksource To: Aleksandar Rikalo , Thomas Bogendoerfer Cc: Aleksandar Rikalo , Chao-ying Fu , Geert Uytterhoeven , Greg Ungerer , Hauke Mehrtens , Ilya Lipnitskiy , Jiaxun Yang , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, Marc Zyngier , Paul Burton , Peter Zijlstra , Serge Semin , Thomas Gleixner , Tiezhu Yang References: <20240511104341.151550-1-aleksandar.rikalo@syrmia.com> <20240511104341.151550-8-aleksandar.rikalo@syrmia.com> Content-Language: en-US From: Daniel Lezcano In-Reply-To: <20240511104341.151550-8-aleksandar.rikalo@syrmia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 11/05/2024 12:43, Aleksandar Rikalo wrote: > From: Paul Burton > > 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 > Signed-off-by: Chao-ying Fu > Signed-off-by: Dragan Mladjenovic > Signed-off-by: Aleksandar Rikalo > --- Applied patch 7 and 8 Thanks -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog