linux-kernel - Re: [PATCH v2 5/7] ARM: perf_event: Fully support Krait CPU PMU events

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Date:	Wed, 22 Jan 2014 12:47:58 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Will Deacon <will.deacon@....com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Neil Leeder <nleeder@...eaurora.org>,
	Ashwin Chaugule <ashwinc@...eaurora.org>
Subject: Re: [PATCH v2 5/7] ARM: perf_event: Fully support Krait CPU PMU events

On 01/21/14 10:37, Stephen Boyd wrote:
> On 01/21/14 10:07, Will Deacon wrote:
>> Do you need isbs to ensure the pmresrn side-effects have happened, or are
>> the registers self-synchronising? Similarly for your other IMP DEF
>> registers.
> There aren't any isbs in the downstream android sources so I assume
> they're self synchronizing. I'll confirm with the CPU designers to make
> sure.
>

CPU folks say no need for isb. They mentioned that the lack of an isb
after the armv7_pmnc_enable_counter() call will leave the action of
enabling the counter "in-flight". The window is probably pretty short on
an SMP kernel because of the spin_unlock right after with the barriers
in it, but the same can't be said for a UP kernel.

Also, the fuzzer didn't find anything else, but I found a bug in the
bitmap logic, updated and reran the fuzzer this morning. Everything
looks good.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

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