[PATCH v8 00/10] misc: Move AMD side band interface(SBI) functionality

Akshay Gupta
2025-04-11T13:31:43Z

At present, sbrmi driver under hwmon subsystem, is probed as an i2c driver,
fetches data using APML specified protocol and reports through hwmon power sensor.

AMD provides additional information using custom protocols, which cannot be
enumerated as hwmon sensors. Hence, move the existing functionality from hwmon/
to misc/ and add support for following custom protocols
- read Processor feature capabilities and configuration information
through side band.
- read Machine Check Architecture(MCA) registers over sideband.
The information is accessed for range of MCA registers by passing
register address and thread ID to the protocol.

NOTE: AMD defines Advanced Platform Management Link (APML) interface which provides
system management functionality access to the baseboard management
controller (BMC).

This patchset is an attempt to keep all APML core functionality in one place,
provide hwmon and IOCTL interface to user space
1. [Patch 1] Move the i2c client probe, hwmon sensors and sbrmi core functionality
from drivers/hwmon to drivers/misc/
2. [Patch 2] Move sbrmi core functionality to new core file to export core functionality
3. [Patch 3] Move hwmon device sensor as separate entity
4. [Patch 4] Convert i2c to regmap which provides multiple benefits
over direct smbus APIs.
a. i2c/i3c support and
b. 1 byte/2 byte RMI register size addressing
5. [Patch 5] Optimize wait condition with regmap API regmap_read_poll_timeout as per
suggestion from Arnd
6. [Patch 6] Register a misc device which provides
a. An ioctl interface through node /dev/sbrmiX
b. Register sets is common across APML protocols. IOCTL is providing
synchronization among protocols as transactions may create
race condition.
7. [Subsequent patches 7, 8 and 9] add support for AMD custom protocols through additional IOCTLs
a. CPUID
b. MCAMSR
c. Register xfer
8. [Patch 10] AMD side band description document

Open-sourced and widely used [1]_ will continue to provide user-space programmable API.

.. [1] https://github.com/amd/esmi_oob_library

*** BLURB HERE ***

Akshay Gupta (10):
hwmon/misc: amd-sbi: Move core sbrmi from hwmon to misc
misc: amd-sbi: Move protocol functionality to core file
misc: amd-sbi: Move hwmon device sensor as separate entity
misc: amd-sbi: Use regmap subsystem
misc: amd-sbi: Optimize the wait condition for mailbox command
completion
misc: amd-sbi: Add support for AMD_SBI IOCTL
misc: amd-sbi: Add support for CPUID protocol
misc: amd-sbi: Add support for read MCA register protocol
misc: amd-sbi: Add support for register xfer
misc: amd-sbi: Add document for AMD SB IOCTL description

Documentation/misc-devices/amd-sbi.rst | 99 ++++
Documentation/misc-devices/index.rst | 1 +
.../userspace-api/ioctl/ioctl-number.rst | 2 +
drivers/hwmon/Kconfig | 10 -
drivers/hwmon/sbrmi.c | 357 -------------
drivers/misc/Kconfig | 1 +
drivers/misc/Makefile | 1 +
drivers/misc/amd-sbi/Kconfig | 18 +
drivers/misc/amd-sbi/Makefile | 4 +
drivers/misc/amd-sbi/rmi-core.c | 474 ++++++++++++++++++
drivers/misc/amd-sbi/rmi-core.h | 74 +++
drivers/misc/amd-sbi/rmi-hwmon.c | 120 +++++
drivers/misc/amd-sbi/rmi-i2c.c | 133 +++++
include/uapi/misc/amd-apml.h | 152 ++++++
14 files changed, 1079 insertions(+), 367 deletions(-)
create mode 100644 Documentation/misc-devices/amd-sbi.rst
delete mode 100644 drivers/hwmon/sbrmi.c
create mode 100644 drivers/misc/amd-sbi/Kconfig
create mode 100644 drivers/misc/amd-sbi/Makefile
create mode 100644 drivers/misc/amd-sbi/rmi-core.c
create mode 100644 drivers/misc/amd-sbi/rmi-core.h
create mode 100644 drivers/misc/amd-sbi/rmi-hwmon.c
create mode 100644 drivers/misc/amd-sbi/rmi-i2c.c
create mode 100644 include/uapi/misc/amd-apml.h

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2.25.1