[PATCH v6 0/6] SMP and CPU hotplug support for Meson8/Meson8b

[Martin Blumenstingl]

This patchset adds support for booting the secondary CPU cores (and
taking them offline again) on Amlogic Meson8 and Meson8b SoCs.
It is based on an earlier version from Carlo Caione - this helped me
a lot to get a better understanding of how SMP/CPU hotplug works
(compared to the code found in Amlogic's GPL kernel sources from
year 2015).


Changes since v5 from [5]:
- dropped dependency on another patch series (for the clock
  controller's embedded reset controller, which is needed to boot
  the secondary CPUs) from the cover-letter as that series is now
  merged
- fix incorrect documentation of scu_cpu_power_enable (thanks to
  Russell King for spotting these). removed the paragraph about
  preemption, cache coherency and interrupts as we're powering on
  a CPU core (the text was copied from the original scu_power_mode
  but simply not adjusted). also changed "Set the executing CPUs"
  to "Set the given (logical) CPU's" as we're not modifying the
  current CPU. this affects only patch #2
- extended the commit message of patch #3 with a short sentence
  about why SCU_CPU_STATUS_MASK was introduced

Changes since v4 from [4]:
- use __pa_symbol(secondary_startup) instead of
  virt_to_phys(secondary_startup) as suggested by Florian Fainelli
  (affects patch #4)
- (cover-letter) removed dependency on my other patch
  "ARM: dts: meson: add a node which describes the SRAM" [2] as that
  was merged into Kevin's Amlogic repo today
- dropped patch #5 ("clk: meson: meson8b: export the CPU soft reset
  lines") again because the reset controller series exposes the
  preprocessor macros now directly, see [1]
- refreshed the .dts patches so they now include the new header for
  the reset line preprocessor macros

Changes since v3 from [3]:
- added Rob's ACK to patch #1
- replaced a msleep(10) with usleep_range(10000, 15000) in patch #4
- removed all "pen" code from patch #4 as that code was not needed
  at all (it was left-over while trying to fix Meson8 secondary CPU
  boot - which turned out to have nothing to do with this "pen" code)
- removed all memory barrier operations as they were added based on
  the code in the Amlogic GPL kernel tree (while trying to fix the
  Meson8 secondary CPU boot - just like the "pen" code). Everything
  still works fine with these on my Meson8m2 and Meson8b boards.
- added PATCH #5 as we now have to export the reset identifiers
  (just like we do it with the clock identifiers / preprocessor
  macros) - this is the result of a change in the reset controller
  patch in version 2, see [1]
- use the reset line preprocessor macros (from patch #5) in patches
  #6 and #7

Changes since v2 from [0]:
- added support for Meson8 (which requires a slightly different
  enable-method)
- implemented CPU hotplug support which allows taking a CPU core
  offline for both, Meson8 and Meson8b
- add a function to smp_scu.c which allows enabling a CPU core from
  a different CPU (previously only the power mode for the current CPU
  could be changed). Without this the CPU cores on Meson8 won't come
  up (Amlogic's vendor GPL kernel sources also enable power through
  SCU as very first step for Meson8b as well)
- add a function to smp_scu.c to get the power status of a CPU core
  (which is needed because the code in .cpu_kill needs to wait until
  the core is actually powered off)
- dropped patch "ARM: DTS: meson8b: Extend L2 cache controller node"
  as it is already applied (for both, Meson8 and Meson8b)
- dropped the patches which implement the reset controller which is
  built into the clock-controller, these are a separate series: [1]
- moved the enable-method property to each CPU node


[0] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-December/390355.html
[1] http://lists.infradead.org/pipermail/linux-amlogic/2017-July/004456.html
[2] http://lists.infradead.org/pipermail/linux-amlogic/2017-July/004282.html
[3] http://lists.infradead.org/pipermail/linux-amlogic/2017-July/004297.html
[4] http://lists.infradead.org/pipermail/linux-amlogic/2017-July/004354.html
[5] http://lists.infradead.org/pipermail/linux-amlogic/2017-July/004460.html

Carlo Caione (2):
  dt-bindings: Amlogic: Add Meson8 and Meson8b SMP related documentation
  ARM: dts: meson8b: add support for booting the secondary CPU cores

Martin Blumenstingl (4):
  ARM: smp_scu: add a helper for powering on a specific CPU
  ARM: smp_scu: allow the platform code to read the SCU CPU status
  ARM: meson: Add SMP bringup code for Meson8 and Meson8b
  ARM: dts: meson8: add support for booting the secondary CPU cores

 .../devicetree/bindings/arm/amlogic/pmu.txt        |  18 +
 .../devicetree/bindings/arm/amlogic/smp-sram.txt   |  32 ++
 Documentation/devicetree/bindings/arm/cpus.txt     |   2 +
 arch/arm/Makefile                                  |   1 +
 arch/arm/boot/dts/meson8.dtsi                      |  21 +
 arch/arm/boot/dts/meson8b.dtsi                     |  21 +
 arch/arm/include/asm/smp_scu.h                     |  12 +
 arch/arm/kernel/smp_scu.c                          |  43 +-
 arch/arm/mach-meson/Kconfig                        |   1 +
 arch/arm/mach-meson/Makefile                       |   1 +
 arch/arm/mach-meson/platsmp.c                      | 440 +++++++++++++++++++++
 11 files changed, 586 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/arm/amlogic/pmu.txt
 create mode 100644 Documentation/devicetree/bindings/arm/amlogic/smp-sram.txt
 create mode 100644 arch/arm/mach-meson/platsmp.c

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2.14.1