[PATCH stable/v4.2.y] ARM: ux500: simplify secondary CPU boot

[Olof Johansson]

On Fri, Oct 23, 2015 at 1:09 AM, Linus Walleij <linus.walleij at linaro.org> wrote:
> On Fri, Oct 23, 2015 at 3:22 AM, Greg KH <greg at kroah.com> wrote:
>> On Thu, Oct 22, 2015 at 06:15:04PM -0700, Kevin Hilman wrote:
>>> On Thu, Oct 22, 2015 at 5:17 PM, Greg KH <greg at kroah.com> wrote:
>>> > On Thu, Oct 22, 2015 at 03:56:08PM -0700, Kevin Hilman wrote:
>>> >> From: Linus Walleij <linus.walleij at linaro.org>
>>> >>
>>> >> This removes a lot of ancient cruft from the Ux500 SMP boot.
>>> >> Instead of the pen grab/release, just point the ROM to
>>> >> secondary_boot() and start the second CPU there, then send
>>> >> the IPI.
>>> >>
>>> >> Use our own SMP enable method. This enables us to remove the
>>> >> last static mapping and get both CPUs booting properly.
>>> >>
>>> >> Tested this and it just works.
>>> >>
>>> >> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
>>> >> Signed-off-by: Olof Johansson <olof at lixom.net>
>>> >> (cherry picked from commit c00def71efd919e8ae835a25f4f4c80a4b2d36d3)
>>> >> Cc: <stable at vger.kernel.org> # v4.2+
>>> >> Signed-off-by: Kevin Hilman <khilman at linaro.org>
>>> >> ---
>>> >> This patch was the 2nd in a 2-patch series.  Only the 1st patch made it
>>> >> into v4.2, but this one is also needed for booting on the ste-snowball.
>>> >>
>>> >>  arch/arm/mach-ux500/Makefile     |   2 +-
>>> >>  arch/arm/mach-ux500/cpu-db8500.c |   1 -
>>> >>  arch/arm/mach-ux500/headsmp.S    |  37 -----------
>>> >>  arch/arm/mach-ux500/platsmp.c    | 132 ++++++++++++---------------------------
>>> >>  arch/arm/mach-ux500/setup.h      |   1 -
>>> >>  5 files changed, 40 insertions(+), 133 deletions(-)
>>> >>  delete mode 100644 arch/arm/mach-ux500/headsmp.S
>>> >
>>> > This looks to me like a "new feature", is it a regression from something
>>> > that used to work in 4.1?
>>>
>>> I guess Linus W. will have to explain better, but I'll try...
>>>
>>> it's the 2nd part of a 2-part fix that was submitted for v4.2, but
>>> only the 1st part made it in because it was late for the merge window.
>>
>> That doesn't really sound like Documentation/stable_kernel_rules.txt
>> material...
>
> It is. Both patches *should* have gone in the merge window, but
> because of a misunderstanding and oversight, one of them were
> missed, so half of the two-part solution was merged, and unfortunately
> merging half of it boot-regressed the platform.

I remember discussing the fact that ux500 is only really used in boot
farms with mainline these days, so we went with the minimal change for
4.2 (which meant no SMP functionality), with the proper fix for 4.3
due to risk/size. This was unfortunately done off-list, so I can't
give you a link. Still, Linus and Tyler both agreed that it didn't
seem warranted to fix urgently for 4.2 (and thus, I'd say, for
-stable)

So, I'm a little surprised to see this go to stable now.


-Olof