[PATCH v6 0/6] Hardware Reduced Mode Cleanup for ACPI

[al.stone at linaro.org]

From: Al Stone <al.stone at linaro.org>

This series of patches starts with Hanjun's patch to create a kernel
config item for CONFIG_ACPI_REDUCED_HARDWARE [0].  Building on that, I
then reviewed all of the code that touched any of several fields in the
FADT that the OSPM is supposed to ignore when ACPI is in Hardware Reduced
mode [1].  Any time there was a use of one of the fields to be ignored,
I evaluated whether or not the code was implementing Hardware Reduced
mode correctly.  Similarly, for each the flags in the FADT flags field
that are to be ignored in Hardware Reduced mode, the kernel code was again
scanned for proper usage.  The remainder of the patches are to fix all of
the situations I could find where the kernel would not behave correctly
in this ACPI mode.

These seem to work just fine on the RTSM model for ARMv7, both with and
without ACPI enabled, and with and without ACPI_REDUCED_HARDWARE enabled;
similarly for the FVP model for ARMv8.  The patches for ACPI on ARM
hardware have been submitted elsewhere but they presume that reduced HW
mode is functioning correctly.  In the meantime, there's no way I can think
of to test all possible scenarios so feedback would be greatly appreciated.


[0] List at https://wiki.linaro.org/LEG/Engineering/Kernel/ACPI/AcpiReducedHw#Section_5:_ACPI_Software_Programming_Model
[1] Please see the ACPI Specification v5.0 for details on Hardware Reduced
    mode (sections 3.11.1, 4.1, 5.2.9, at a minimum).

Changes for v6:
   -- Allow selection of CONFIG_ACPI_REDUCED_HARDWARE_ONLY to be more
      architecture-independent, but make it harder to accidentally enable.
   -- Make sure that ACPI ECs do not use the ACPI global lock when in
      hardware reduced mode (I had missed this case in earlier reviews
      of the kernel tree).

Changes for v5:
   -- Clarify that if the kernel config option to build ACPI hardware reduced
      mode is used, it builds a hardware reduced *only* kernel (i.e., full
      legacy ACPI mode will no longer work).

Changes for v4:
   -- Given the current state of ACPICA, disable CONFIG_ACPI_REDUCED_HARDWARE
      for use on anything other than ARM.
   -- Replaced #ifdefs with run-time checking for hardware reduced mode,
      whenever possible

Changes for v3:
   -- Modified enabling ACPI_REDUCED_HARDWARE in ACPICA when using
      kernel config item CONFIG_ACPI_REDUCED_HARDWARE; now consistent
      with ACPICA code base where needed
   -- Enable X86 for CONFIG_ACPI_REDUCED_HARDWARE
   -- Minimize bus master reload patching
   -- Remove unneeded patch for dmi_check_system() (was 4/6)
   -- Correct the patch for removing unneeded map/unmap of FADT fields

Changes for v2:
   -- Remove patch that was outside of reduced HW mode changes
   -- Simplify CONFIG_ACPI_REDUCED_HARDWARE in Kconfig
   -- Simplify use of CONFIG_ACPI_REDUCED_HARDWARE in #ifdefs
   -- Ensure changelogs are present
   -- Combine and simplify previous patches 8 & 10


Al Stone (6):
  ACPI: introduce CONFIG_ACPI_REDUCED_HARDWARE_ONLY to enforce this ACPI
    mode
  ACPI: bus master reload not supported in reduced HW mode
  ACPI: HW reduced mode does not allow use of the FADT sci_interrupt
    field
  ACPI: in HW reduced mode, using FADT PM information is not allowed.
  ACPI: do not map/unmap memory regions for FADT entries in reduced HW
    mode
  ACPI: make sure ECs do not use the ACPI global lock

 drivers/acpi/Kconfig            | 12 ++++++++++++
 drivers/acpi/bus.c              | 30 ++++++++++++++++--------------
 drivers/acpi/ec.c               | 12 ++++++++++--
 drivers/acpi/osl.c              | 38 +++++++++++++++++++-------------------
 drivers/acpi/pci_link.c         |  2 ++
 drivers/acpi/processor_idle.c   | 14 ++++++++++++--
 include/acpi/platform/aclinux.h |  6 ++++++
 7 files changed, 77 insertions(+), 37 deletions(-)

-- 
1.8.4.2