linux-kernel - Re: [PATCH v3 RESEND 2/5] ARM: add SMP support for Broadcom mobile SoCs

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Message-ID: <20140515182620.GN32082@beef>
Date:	Thu, 15 May 2014 14:26:20 -0400
From:	Matt Porter <mporter@...aro.org>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	Alex Elder <elder@...aro.org>, Christian Daudt <bcm@...thebug.org>,
	Russell King <linux@....linux.org.uk>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>, sboyd@...eaurora.org,
	bcm-kernel-feedback-list@...adcom.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 RESEND 2/5] ARM: add SMP support for Broadcom mobile
 SoCs

On Thu, May 15, 2014 at 11:03:49AM -0700, Florian Fainelli wrote:
> Hi Alex,
> 
> 2014-05-15 10:58 GMT-07:00 Alex Elder <elder@...aro.org>:
> > This patch adds SMP support for BCM281XX and BCM21664 family SoCs.
> >
> > This feature is controlled with a distinct config option such that a
> > SMP-enabled multi-v7 binary can be configured to run these SoCs in
> > uniprocessor mode.  Since this SMP functionality is used for
> > multiple Broadcom mobile chip families the config option is called
> > ARCH_BCM_MOBILE_SMP (for lack of a better name).
> >
> > On SoCs of this type, the secondary core is not held in reset on
> > power-on.  Instead it loops in a ROM-based holding pen.  To release
> > it, one must write into a special register a jump address whose
> > low-order bits have been replaced with a secondary core's id, then
> > trigger an event with SEV.  On receipt of an event, the ROM code
> > will examine the register's contents, and if the low-order bits
> > match its cpu id, it will clear them and write the value back to the
> > register just prior to jumping to the address specified.
> >
> > The location of the special register is defined in the device tree
> > using a "secondary-boot-reg" property in a node whose "enable-method"
> > matches.
> >
> > Derived from code originally provided by Ray Jui <rjui@...adcom.com>
> >
> > Signed-off-by: Alex Elder <elder@...aro.org>
> > ---
> >  arch/arm/mach-bcm/Kconfig   |  18 +++-
> >  arch/arm/mach-bcm/Makefile  |   3 +
> >  arch/arm/mach-bcm/platsmp.c | 201 ++++++++++++++++++++++++++++++++++++++++++++
> 
> Could we make that name a little bit more specific to the mobile SoCs?
> There are other BCM SoCs either currently supported in this directory
> (BCM5310X), or making their way to be supported (brcmstb, bcm63xx),
> and those share nothing with the Mobile SoC SMP code.
 
Right.

> Maybe we should create another level directory within mach-bcm...

Let's not go that far. The general direction we need to go is to work
toward removing this code from mach-bcm/ completely. I don't really want
to see us adding directories and encouraging burying a lot of new files
in them.

A unique name will be enough and then we can work toward moving things
out to drivers/ over time.

-Matt
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