[PATCH v7 0/3] Add SSIF BMC driver

[Quan Nguyen <quan@os.amperecomputing.com>]

This series add support the SSIF BMC driver which is to perform in-band
IPMI communication with their host in management (BMC) side.

SSIF BMC driver in this series is tested with Aspeed AST2500.

Discussion for v6: https://lkml.org/lkml/2022/3/10/340

v7:
  + Remove unnecessary del_timer() in response_timeout()        [Corey]
  + Change compatible string from "ampere,ssif-bmc" to "ssif-bmc"  [Jae]
  + Dropped the use of ssif_msg_len() macro, use the len directly [Quan]
  + Solve possible issue if both response timer and ssif_bmc_write()
  occurred at the same time                                      [Corey]
  + Fix wrong return type of ssif_bmc_poll()         [kernel robot test]
  + Refactor and introduce ssif_part_buffer struct to replace the
  response_buf to manage each send/receive part of ssif           [Quan]
  + Change SSIF_BAD_SMBUS state to SSIF_ABORTING state           [Corey]
  + Support abort feature to skip the current bad request/response and
  wait until next new request                                    [Corey]
  + Refactor the PEC calculation to avoid the re-calculate the PEC on
  each I2C_SLAVE_WRITE_RECEIVED event                             [Quan]
  + Fix the use of error-proned idx                              [Corey]
  + Defer the test for valid SMBus command until the read/write part
  is determined                                                   [Quan]
  + Change/split unsupported_smbus_cmd() to
  supported_[write|read]_cmd()                                   [Corey]
  + Abort the request if somehow its size exceeded 255 bytes      [Quan]

v6:
  + Drop the use of slave_enable()                             [Wolfram]
  + Make i2c-aspeed to issue RxCmdLast command on all
  I2C_SLAVE_WRITE_REQUESTED event to assert NAK when slave busy   [Quan]
  + Make i2c slave to return -EBUSY when it's busy                [Quan]
  + Drop the aborting feature as return Completion Code 0xFF may stop
  host to retry and make ipmi_ssif.so fails to load               [Quan]
  + Add timer to recover slave from busy state when no response   [Quan]
  + Clean request/response buffer appropriately                   [Quan]
  + Add some minor change on error and warning messages           [Quan]

v5:
  + Correct the patches order to fix the bisect issue found by
  kernel build robot

v4:
  + Fix recursive spinlock                                      [Graeme]
  + Send response with Completion code 0xFF when aborting         [Quan]
  + Fix warning with dt_binding_check                              [Rob]
  + Change aspeed-ssif-bmc.yaml to ssif-bmc.yaml                  [Quan]
  + Added bounding check on SMBus writes and the whole request     [Dan]
  + Moved buffer to end of struct ssif_bmc_ctx to avoid context
    corruption if somehow buffer is written past the end           [Dan]
  + Return -EINVAL if userspace buffer too small, don't
    silence truncate                                       [Corey, Joel]
  + Not necessary to check NONBLOCK in lock                      [Corey]
  + Enforce one user at a time                                    [Joel]
  + Reject write with invalid response length from userspace     [Corey]
  + Add state machines for better ssif bmc state handling         [Quan]
  + Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
    SSIF BMC driver                                               [Quan]
  + Change compatible string "aspeed,ast2500-ssif-bmc" to
    "ampere,ssif-bmc"                                             [Quan]
  + Toggle Slave enable in i2c-aspeed to turn on/off slave mode   [Ryan]
  + Added slave_enable() to struct i2c_algorithm to control
    slave mode and to address the recursive spinlock      [Graeme, Ryan]
  + Abort current request with invalid SMBus write or
    invalid command                                               [Quan]
  + Abort all request if there is pending response                [Quan]
  + Changed validate_pec() to validate_request()                  [Quan]
  + Add unsupported_smbus_cmd() to handle unknown SMBus command   [Quan]
  + Print internal state string for ease investigating issue      [Quan]
  + Move to READY state on SLAVE_STOP event                       [Quan]
  + Change initilize_transfer() to process_smbus_cmd()            [Quan]
  + Introduce functions for each slave event                      [Quan]

v3:
  + Switched binding doc to use DT schema format                   [Rob]
  + Splited into generic ssif_bmc and aspeed-specific      [Corey, Joel]
  + Removed redundant license info                                [Joel]
  + Switched to use traditional if-else                           [Joel]
  + Removed unused ssif_bmc_ioctl()                               [Joel]
  + Made handle_request()/complete_response() to return void      [Joel]
  + Refactored send_ssif_bmc_response() and
  receive_ssif_bmc_request()                                     [Corey]
  + Remove mutex                                                 [Corey]
  + Use spin_lock/unlock_irqsave/restore in callback             [Corey]
  + Removed the unnecessary memset                               [Corey]
  + Switch to use dev_err()                                      [Corey]
  + Combine mask/unmask two interrupts together                  [Corey]
  + Fixed unhandled Tx done with NAK                              [Quan]
  + Late ack'ed Tx done w/wo Ack irq                              [Quan]
  + Use aspeed-specific exported aspeed_set_slave_busy() when
  slave busy to fix the deadlock                 [Graeme, Philipp, Quan]
  + Clean buffer for last multipart read                          [Quan]
  + Handle unknown incoming command                               [Quan]

v2:
  + Fixed compiling error with COMPILE_TEST for arc

Quan Nguyen (3):
  ipmi: ssif_bmc: Add SSIF BMC driver
  bindings: ipmi: Add binding for SSIF BMC driver
  i2c: aspeed: Assert NAK when slave is busy

 .../devicetree/bindings/ipmi/ssif-bmc.yaml    |  38 +
 drivers/char/ipmi/Kconfig                     |  11 +
 drivers/char/ipmi/Makefile                    |   1 +
 drivers/char/ipmi/ssif_bmc.c                  | 780 ++++++++++++++++++
 drivers/char/ipmi/ssif_bmc.h                  | 107 +++
 drivers/i2c/busses/i2c-aspeed.c               |   5 +-
 6 files changed, 941 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/ipmi/ssif-bmc.yaml
 create mode 100644 drivers/char/ipmi/ssif_bmc.c
 create mode 100644 drivers/char/ipmi/ssif_bmc.h

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2.35.1