From: peterz@infradead.org
To: Leo Yan <leo.yan@linaro.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Ingo Molnar <mingo@redhat.com>, Wei Li <liwei391@huawei.com>,
Al Grant <al.grant@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kemeng Shi <shikemeng@huawei.com>,
Ian Rogers <irogers@google.com>,
John Garry <john.garry@huawei.com>,
Stephane Eranian <eranian@google.com>,
Nick Gasson <nick.gasson@arm.com>,
Andi Kleen <ak@linux.intel.com>,
Steve MacLean <Steve.MacLean@Microsoft.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Kan Liang <kan.liang@linux.intel.com>,
Will Deacon <will@kernel.org>, James Clark <james.clark@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/6] perf tsc: Add rdtsc() for Arm64
Date: Wed, 2 Sep 2020 15:48:05 +0200 [thread overview]
Message-ID: <20200902134805.GI1362448@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200902132131.36304-3-leo.yan@linaro.org>
On Wed, Sep 02, 2020 at 02:21:27PM +0100, Leo Yan wrote:
> The system register CNTVCT_EL0 can be used to retrieve the counter from
> user space. Add rdtsc() for Arm64.
> +u64 rdtsc(void)
> +{
> + u64 val;
Would it make sense to put a comment in that this counter is/could-be
'short' ? Because unlike x86-TSC, this thing isn't architecturally
specified to be 64bits wide.
> + asm volatile("mrs %0, cntvct_el0" : "=r" (val));
> +
> + return val;
> +}
> --
> 2.17.1
>
next prev parent reply other threads:[~2020-09-02 14:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-02 13:21 [PATCH v3 0/6] Perf tool: Support TSC for Arm64 Leo Yan
2020-09-02 13:21 ` [PATCH v3 1/6] perf tsc: Move out common functions from x86 Leo Yan
2020-09-02 13:21 ` [PATCH v3 2/6] perf tsc: Add rdtsc() for Arm64 Leo Yan
2020-09-02 13:48 ` peterz [this message]
2020-09-03 2:23 ` Leo Yan
2020-09-04 19:08 ` Arnaldo Carvalho de Melo
2020-09-02 13:21 ` [PATCH v3 3/6] perf tsc: Calculate timestamp with cap_user_time_short Leo Yan
2020-09-02 13:21 ` [PATCH v3 4/6] perf tsc: Support cap_user_time_short for event TIME_CONV Leo Yan
2020-09-02 13:21 ` [PATCH v3 5/6] perf tests tsc: Make tsc testing as a common testing Leo Yan
2020-09-02 13:21 ` [PATCH v3 6/6] perf tests tsc: Add checking helper is_supported() Leo Yan
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