linux-kernel - Re: [PATCH RESEND 0/4] SMP support for Broadcom NSP

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Date:	Fri, 6 Nov 2015 17:39:43 +0530
From:	Kapil Hali <kapilh@...adcom.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	"Mark Rutland" <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Jon Mason <jonmason@...adcom.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	"Gregory Fong" <gregory.0xf0@...il.com>,
	Lee Jones <lee@...nel.org>, Hauke Mehrtens <hauke@...ke-m.de>,
	Heiko Stuebner <heiko@...ech.de>,
	Kever Yang <kever.yang@...k-chips.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Olof Johansson <olof@...om.net>,
	"Paul Walmsley" <paul@...an.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Chen-Yu Tsai <wens@...e.org>, <devicetree@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	<bcm-kernel-feedback-list@...adcom.com>
Subject: Re: [PATCH RESEND 0/4] SMP support for Broadcom NSP



On 11/5/2015 3:04 PM, Russell King - ARM Linux wrote:
> On Thu, Nov 05, 2015 at 12:51:17AM -0500, Kapil Hali wrote:
>> Hi,
>>
>> This series adds SMP support for Broadcom's Northstar Plus SoC.
>>
>> There are similar SMP enablement methods for many ARMv7 bsed SoCs.
>> BCM NSP SoC, has a typical such mechanism - after power-on, the
>> secondary core is held in a standby state, primary core provides a
>> startup address for the secondary core and wakes it up. Booting of
>> the secondary core is serialized using pen_release global variable.
> 
> Why do you need the pen_release stuff?  The above implies that you
> have only one secondary core, and you can control when it comes out
> of standby state.
> 
We can initiate a wake-up of the secondary core. I tested the changes
without pen_release method and it works. However, as I understand, I
think there is no other way for the primary core to know if the 
secondary core has come out of standby state other than pen_release
mechanism. When there is no other method available, will not 
smp_boot_secondary() always return successful wake-up of the
secondary core?

> Please, don't assume that the pen_release stuff is any kind of recommended
> or standardised system.  It isn't.  It's a hack for ARMs evaluation
> platforms.
> 
Got it. As pen_release is forbidden, I will change the SMP mechanism
to remove pen_release method in the new patch set.

Thanks,
Kapil

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