linux-kernel - Re: [PATCH] ARM: bcm2836: Send event when onlining other cores

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Date:   Tue, 15 Aug 2017 11:04:01 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Stefan Wahren <stefan.wahren@...e.com>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     Phil Elwell <phil@...pberrypi.org>,
        Scott Branden <sbranden@...adcom.com>,
        Ray Jui <rjui@...adcom.com>,
        Russell King <linux@...linux.org.uk>,
        linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: bcm2836: Send event when onlining other cores

Stefan Wahren <stefan.wahren@...e.com> writes:

> Hi Eric,
>
>> Stefan Wahren <stefan.wahren@...e.com> hat am 14. August 2017 um 19:11 geschrieben:
>> 
>> 
>> Hi Florian,
>> 
>> > Florian Fainelli <f.fainelli@...il.com> hat am 14. August 2017 um 18:25 geschrieben:
>> > 
>> > 
>> > 
>> > 
>> > On 08/08/2017 04:04 AM, Phil Elwell wrote:
>> > > Secondary cores should enter a low-power idle state when waiting to
>> > > be started. The "wfe" instruction causes a core to wait until an event
>> > > or interrupt arrives before continuing to the next instruction, and
>> > > the "sev" instruction sends a wakeup event to the other cores.
>> > > 
>> > > Add an "sev" (and a memory barrier) to bcm2836_boot_secondary, the
>> > > function that wakes the waiting cores during booting. This is required
>> > > if the secondary cores are sitting in "wfe", and harmless if not.
>> > 
>> > Eric, should I just pick this up for the upcoming ARM SoC pull requests
>> > that I am preparing, or do you have more changes aside from the two tags
>> > I already merged?
>> 
>> this patch depends on series "ARM: bcm2836: Move SMP startup code to arch/arm".
>> 
>> I didn't had the time to test Phil's patch in all relevant cases. But i could at least prepare a branch with my changes with the acks.
>
> i prepared the branches bcm2835-dt-next-v2 and bcm2835-soc-next.

bcm2835-soc-next on its own breaks boot for me on the Pi2, so I had to
merge in the DT branch first.  I've rebased to do that, pulled in this
patch (and the clk one), and sent PRs for -dt and -soc.

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