linux-kernel - Re: [PATCH v8 01/11] ARM: brcmstb: add infrastructure for ARM-based Broadcom STB SoCs

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Date:	Wed, 30 Jul 2014 19:36:35 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Matt Porter <mporter@...aro.org>,
	Christian Daudt <bcm@...thebug.org>,
	linux-arm-kernel@...ts.infradead.org,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	devicetree@...r.kernel.org, Gregory Fong <gregory.0xf0@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Marc Carino <marc.ceeeee@...il.com>
Subject: Re: [PATCH v8 01/11] ARM: brcmstb: add infrastructure for ARM-based
 Broadcom STB SoCs

Hi Russell,

On Wed, Jul 30, 2014 at 10:26:35AM +0100, Russell King wrote:
> On Mon, Jul 21, 2014 at 02:07:56PM -0700, Brian Norris wrote:
> > +static DEFINE_SPINLOCK(boot_lock);
> > +
> > +static void brcmstb_secondary_init(unsigned int cpu)
> > +{
> > +	/*
> > +	 * Synchronise with the boot thread.
> > +	 */
> > +	spin_lock(&boot_lock);
> > +	spin_unlock(&boot_lock);
> > +}
> > +
> > +static int brcmstb_boot_secondary(unsigned int cpu, struct task_struct *idle)
> > +{
> > +	/*
> > +	 * set synchronisation state between this boot processor
> > +	 * and the secondary one
> > +	 */
> > +	spin_lock(&boot_lock);
> > +
> > +	/* Bring up power to the core if necessary */
> > +	if (brcmstb_cpu_get_power_state(cpu) == 0)
> > +		brcmstb_cpu_power_on(cpu);
> > +
> > +	brcmstb_cpu_boot(cpu);
> > +
> > +	/*
> > +	 * now the secondary core is starting up let it run its
> > +	 * calibrations, then wait for it to finish
> > +	 */
> > +	spin_unlock(&boot_lock);
> 
> I've just read through this code (because it caused my allmodconfig to
> break) and spotted this.

Sorry about the allmodconfig problems. I never compile-tested with ARMv6
enabled. This look OK?

diff --git a/arch/arm/mach-bcm/Makefile b/arch/arm/mach-bcm/Makefile
index f3665121729b..5ce82b4ba931 100644
--- a/arch/arm/mach-bcm/Makefile
+++ b/arch/arm/mach-bcm/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_ARCH_BCM2835)	+= board_bcm2835.o
 obj-$(CONFIG_ARCH_BCM_5301X)	+= bcm_5301x.o
 
 ifeq ($(CONFIG_ARCH_BRCMSTB),y)
+CFLAGS_platsmp-brcmstb.o	+= -march=armv7-a
 obj-y				+= brcmstb.o
 obj-$(CONFIG_SMP)		+= headsmp-brcmstb.o platsmp-brcmstb.o
 endif

> What function does boot_lock perform here?  Please, don't quote the
> comments (I know where the comments came from) but what I want to hear
> is your comments about why you decided to retain this.

You might glean a little more from my response to Rob, but I'm not sure
there was a good reason for retaining this. We do need to be sure the
CPU is fully powered online before bringing it out of reset, but the
spinlock seems overkill AFAICT.

Brian
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