This patchset adds support for the PCC (Platform Communication Channel) interface as described in the current ACPI 5.0 spec. See Section 14 of the ACPI spec - http://acpi.info/DOWNLOADS/ACPI_5_Errata%20A.pdf for more details on how PCC works.
In brief PCC is a generic means for PCC clients, to talk to the firmware. The PCC register space is typically memory mapped IO and uses a doorbell mechanism to communicate synchronously from the OS to the firmware. The PCC driver is completely agnostic to the protocol implemented by the PCC clients. It only implements the enumeration of PCC channels and the low level transport mechanism and leaves the rest to the PCC clients.
The PCC is meant to be useable in the future by clients such as CPPC (Collaborative Processor Performance Control), RAS (Reliability, Availability and Serviceability) and MPST (Memory Power State Tables) and possibly others.
Changes since V2: - Rebased on top of git://git.linaro.org/landing-teams/working/fujitsu/integration.git branch mailbox-for-3.17 - Added PCC API to mailbox framework as per Arnd's suggestion to allow usage without ACPI.
Changes since V1: -Integration with Mailbox framework - https://lkml.org/lkml/2014/5/15/49
Ashwin Chaugule (3): Mailbox: Add support for PCC mailbox and channels Add support for Platform Communication Channel PCC-test: Test driver to trigger PCC commands
drivers/mailbox/Kconfig | 12 ++ drivers/mailbox/Makefile | 2 + drivers/mailbox/mailbox.c | 118 +++++++++++++++++-- drivers/mailbox/pcc-test.c | 208 +++++++++++++++++++++++++++++++++ drivers/mailbox/pcc.c | 228 +++++++++++++++++++++++++++++++++++++ include/linux/mailbox_client.h | 6 + include/linux/mailbox_controller.h | 1 + 7 files changed, 568 insertions(+), 7 deletions(-) create mode 100644 drivers/mailbox/pcc-test.c create mode 100644 drivers/mailbox/pcc.c