From: Alexander Stein <alexander.stein@systec-electronic.com>
To: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: linux-kernel@vger.kernel.org,
Russell King - ARM Linux <linux@arm.linux.org.uk>,
linux-arm-kernel@lists.infradead.org,
Dave Martin <Dave.Martin@arm.com>,
Doug Anderson <dianders@chromium.org>,
Heiko Stuebner <heiko@sntech.de>,
Nicolas Ferre <nicolas.ferre@atmel.com>
Subject: Re: [PATCH v2 2/2] ARM: at91: pm: switch to the PIE infrastructure
Date: Wed, 29 Jun 2016 10:30:55 +0200 [thread overview]
Message-ID: <1503370.EB259eFnzi@ws-stein> (raw)
In-Reply-To: <20160629075714.GP29249@piout.net>
On Wednesday 29 June 2016 09:57:14, Alexandre Belloni wrote:
> On 29/06/2016 at 08:12:21 +0200, Alexander Stein wrote :
> > > +#if defined(CONFIG_CPU_V7)
> > > + dsb();
> > > + wfi();
> > > +#else
> > > + asm volatile ("mcr p15, 0, %0, c7, c0, 4" \
> > > + : : "r" (0) : "memory");
> > > +#endif
> >
> > Why not defining wfi() for __LINUX_ARM_ARCH__ < 7 as it is done for dsb()
> > and friends in arch/arm/include/asm/barrier.h? So you can get rid of that
> > #if completly.
>
> Well, Russell said it was not useful because "there's no architected WFI
> instruction which doesn't have CPU specific issues (hence why we have
> cpu_do_idle() to abstract that)"
Wouldn't you suffer from this here as well? Anyway, the inline assembly above
is what is actually wfi but using CP15. I checked several proc-*.S in do_idle
and they all have
> "mcr p15, 0, r0, c7, c0, 4 @ Wait for interrupt"
at some point. so this inline assembly could actually be implemented on wfi()
macro.
Best regards,
Alexander
prev parent reply other threads:[~2016-06-29 8:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-28 22:44 [PATCH v2 0/2] Embedding Position Independent Executables Alexandre Belloni
2016-06-28 22:44 ` [PATCH v2 1/2] ARM: PIE infrastructure Alexandre Belloni
2016-06-28 22:44 ` [PATCH v2 2/2] ARM: at91: pm: switch to the " Alexandre Belloni
2016-06-29 6:12 ` Alexander Stein
2016-06-29 7:57 ` Alexandre Belloni
2016-06-29 8:30 ` Alexander Stein [this message]
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