From: Michael Ellerman <mpe@ellerman.id.au>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
svaidy@linux.vnet.ibm.com, Nicholas Piggin <npiggin@gmail.com>
Cc: "Gautham R . Shenoy" <ego@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org,
"Shreyas B . Prabhu" <shreyas@linux.vnet.ibm.com>
Subject: Re: [PATCH 13/14] powerpc/64: runlatch CTRL[RUN] set optimisation
Date: Wed, 14 Jun 2017 13:34:27 +1000 [thread overview]
Message-ID: <87fuf344zg.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <1497361558.2897.12.camel@kernel.crashing.org>
Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> On Tue, 2017-06-13 at 20:04 +1000, Michael Ellerman wrote:
>> > Good idea.=C2=A0 Writing to CTRL register can change only the RUN fiel=
d.
>> > Was this any different in older generations?
>>=20
>> No AFAICS back to 2.02.
>>=20
>> > Anton and Ben kept the mfspr/mtspr part in earlier updates to this
>> > routine.
>>=20
>> Doing the read/modify write is forward compatible vs a new writable
>> field, whereas writing the whole register with a known value is not.
>
> At this stage I wouldn't worry too much about it. What we can do is
> write a pre-cooked value (from reading it earlier once at boot) if we
> are paranoid or just do what Nick does and put the onus on future
> designs that might want to re-use it for other things to add a mode
> bits to configure the new feature in.
Fine by me.
cheers
next prev parent reply other threads:[~2017-06-14 3:34 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-11 23:58 [PATCH 00/14 v2] idle performance improvements Nicholas Piggin
2017-06-11 23:58 ` [PATCH 01/14] powerpc/64s: idle move soft interrupt mask logic into C code Nicholas Piggin
2017-06-12 8:37 ` Gautham R Shenoy
2017-06-12 14:46 ` Nicholas Piggin
2017-06-13 4:28 ` Gautham R Shenoy
2017-06-11 23:58 ` [PATCH 02/14] powerpc/64s: idle hotplug lazy-irq simplification Nicholas Piggin
2017-06-11 23:58 ` [PATCH 03/14] powerpc/64s: idle provide a default idle for POWER9 Nicholas Piggin
2017-06-12 8:53 ` Gautham R Shenoy
2017-06-12 14:46 ` Nicholas Piggin
2017-06-11 23:58 ` [PATCH 04/14] powerpc/64s: idle process interrupts from system reset wakeup Nicholas Piggin
2017-06-12 9:41 ` Gautham R Shenoy
2017-06-12 14:51 ` Nicholas Piggin
2017-06-11 23:58 ` [PATCH 05/14] powerpc/64s: msgclr when handling doorbell exceptions Nicholas Piggin
2017-06-12 14:38 ` Gautham R Shenoy
2017-06-11 23:58 ` [PATCH 06/14] powerpc/64s: interrupt replay balance the return branch predictor Nicholas Piggin
2017-06-12 14:41 ` Gautham R Shenoy
2017-06-13 9:51 ` Michael Ellerman
2017-06-13 11:09 ` Nicholas Piggin
2017-06-11 23:58 ` [PATCH 07/14] powerpc/64s: idle branch to handler with virtual mode offset Nicholas Piggin
2017-06-11 23:58 ` [PATCH 08/14] powerpc/64s: idle avoid SRR usage in idle sleep/wake paths Nicholas Piggin
2017-06-13 10:25 ` Gautham R Shenoy
2017-06-13 10:45 ` Nicholas Piggin
2017-06-11 23:58 ` [PATCH 09/14] powerpc/64s: idle hmi wakeup is unlikely Nicholas Piggin
2017-06-12 15:03 ` Gautham R Shenoy
2017-06-11 23:58 ` [PATCH 10/14] powerpc/64s: cpuidle set polling before enabling irqs Nicholas Piggin
2017-06-12 15:10 ` Gautham R Shenoy
2017-06-12 15:20 ` Nicholas Piggin
2017-06-11 23:58 ` [PATCH 11/14] powerpc/64s: cpuidle read mostly for common globals Nicholas Piggin
2017-06-12 15:30 ` Gautham R Shenoy
2017-06-12 17:50 ` Vaidyanathan Srinivasan
2017-06-11 23:58 ` [PATCH 12/14] powerpc/64s: cpuidle no memory barrier after break from idle Nicholas Piggin
2017-06-12 17:48 ` Vaidyanathan Srinivasan
2017-06-13 12:47 ` Nicholas Piggin
2017-06-11 23:58 ` [PATCH 13/14] powerpc/64: runlatch CTRL[RUN] set optimisation Nicholas Piggin
2017-06-12 17:11 ` Vaidyanathan Srinivasan
2017-06-13 10:04 ` Michael Ellerman
2017-06-13 11:56 ` Nicholas Piggin
2017-06-13 13:45 ` Benjamin Herrenschmidt
2017-06-14 3:34 ` Michael Ellerman [this message]
2017-06-11 23:58 ` [PATCH 14/14] powerpc/64s: idle runlatch switch is done with MSR[EE]=0 Nicholas Piggin
2017-06-12 17:00 ` Vaidyanathan Srinivasan
-- strict thread matches above, loose matches on Subject: below --
2017-06-08 15:50 [PATCH 00/14] idle performance improvements Nicholas Piggin
2017-06-08 15:51 ` [PATCH 13/14] powerpc/64: runlatch CTRL[RUN] set optimisation Nicholas Piggin
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