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

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Date:	Thu, 15 May 2014 11:31:54 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Matt Porter <mporter@...aro.org>
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 <sboyd@...eaurora.org>,
	bcm-kernel-feedback-list <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

2014-05-15 11:26 GMT-07:00 Matt Porter <mporter@...aro.org>:
> 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.

Ok, makes sense.

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

Sounds good, thanks!
-- 
Florian
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