Message-Id: <1396041180-29897-1-git-send-email-elder@linaro.org>
Date:	Fri, 28 Mar 2014 16:12:53 -0500
From:	Alex Elder <elder@...aro.org>
To:	linux@....linux.org.uk, linus.walleij@...aro.org,
	viresh.linux@...il.com, shiraz.hashim@...il.com,
	catalin.marinas@....com
Cc:	spear-devel@...t.st.com, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 0/7] ARM: SMP: common "pen" secondary release method

This series proposes creating a single implementation of the "pen
release" (or spin-table) mechanism for starting secondary CPUs on
ARM SMP systems.  This mechanism is currently implemented at least 5
times in the kernel, each essentially identical to the other.  There
are other machines that use this method, but slight differences make
it necessary to incorporate further work in order to accomodate them
with a single set of functions.

This work began with integrating SMP support for a Broadcom SoC.
The code I started was another copy of the "pen release" code.
Looking at how existing systems handled this, the duplication of
code was obvious, but the fact that implementations were identical
was less so.  In addition, the arm64 (though not 32-bit arm) code
supports the ability to define an "enable-method" property for CPUs
in a machine's device tree (one of which is "spin-table"), allowing
the secondary startup mechanism to be specified abstractly.

My broader goal then was to set up the SMP support for the Broadcom
SoC such that it could be defined in its device tree using a central
"spin-table" enable method for secondary CPUs.  The first step was
to create a central spin-table implementation.  I've tried to do
this generally so it's usable by as many other platforms as
possible.  (An alternative would be to define a custom enable method
for this platform, but I'd prefer to avoid that if I can.)

I already have some code for the second step--which supports
specifying the "spin-table" CPU enable method in device tree files.
But before presenting that I wanted to post this series to get
feedback on the approach.

I've provided a little more information for each patch below.

This code is available in the "review/common-spin-code" branch of
the git repository here:
    http://git.linaro.org/landing-teams/working/broadcom/kernel.git


					-Alex

Alex Elder (7):
  ARM: allow <asm/cputype.h> inclusion from assembly
    This patch is done specifically so the next one can use the
    value of MPIDR_HWID_BITMASK in secondary_holding_pen(), which is
    defined in asssembly.
  ARM: SMP: generic SMP spin-table method routines
    Define the common code (based on any of the others, but
    reportedly they all derive from ARM Realview.)  Names are
    changed to be more like arch/arm64/kernel/smp_spin_table.c.

  ARM: realview: use central SMP spin-table routines
  ARM: vexpress: use central SMP spin-table routines
  ARM: versatile: kill off SMP support code
  	The SMP code for realview and vexpress both use SMP code
	defined under mach-versatile, so these three go together.

  ARM: ux500: use generic SMP spin-table routines
    This one is a pretty straightforward switch to using
    the common code.
  	
  ARM: spear: use central SMP spin-table routines
    This is straightforward as well, but it depends on the
    two prerequisite patches mentioned above (which together
    make this code roughly identical to the rest).

 arch/arm/include/asm/cputype.h                 |    4 ++
 arch/arm/include/asm/smp.h                     |    5 ++
 arch/arm/kernel/head.S                         |   33 +++++++++
 arch/arm/kernel/smp.c                          |   77 ++++++++++++++++++++
 arch/arm/mach-realview/platsmp.c               |    8 +--
 arch/arm/mach-spear/Makefile                   |    2 +-
 arch/arm/mach-spear/generic.h                  |    1 -
 arch/arm/mach-spear/headsmp.S                  |   47 ------------
 arch/arm/mach-spear/platsmp.c                  |   75 +------------------
 arch/arm/mach-ux500/Makefile                   |    2 +-
 arch/arm/mach-ux500/headsmp.S                  |   37 ----------
 arch/arm/mach-ux500/platsmp.c                  |   72 +------------------
 arch/arm/mach-vexpress/platsmp.c               |    8 +--
 arch/arm/mach-vexpress/v2m.c                   |    1 -
 arch/arm/plat-versatile/Makefile               |    1 -
 arch/arm/plat-versatile/headsmp.S              |   41 -----------
 arch/arm/plat-versatile/include/plat/platsmp.h |   14 ----
 arch/arm/plat-versatile/platsmp.c              |   91 ------------------------
 18 files changed, 133 insertions(+), 386 deletions(-)
 delete mode 100644 arch/arm/mach-spear/headsmp.S
 delete mode 100644 arch/arm/mach-ux500/headsmp.S
 delete mode 100644 arch/arm/plat-versatile/headsmp.S
 delete mode 100644 arch/arm/plat-versatile/include/plat/platsmp.h
 delete mode 100644 arch/arm/plat-versatile/platsmp.c

-- 
1.7.9.5

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