Abstract: Embodiments are described for detecting and recovering from an inoperable device management bus. A remote management controller is configured to offload device management bus transactions that use a messaging protocol. The messing protocol transactions are offloaded to a bus protocol controller that is responsible for managing bus operations using the messaging protocol. The bus protocol controller updates a set of bus status counters stored in a shared memory based on the processing of the offloaded messaging protocol transactions. The remote management controller processes device management bus transactions that use a bus protocol and updates the bus status counters based on the status of the bus protocol transactions. The remote management controller determines the status of the device management bus based on the bus status counters in shared memory, if the device management bus is inoperable, resets the remote management controller.

Abstract: Embodiments are described for operating a device management bus coupled to a remote access controller and a managed device. The remote access controller detects an inoperable state of the bus and determines a FRU (Field Replaceable Unit) memory is accessible on the managed device. A predefined reset indicator is written to the FRU memory. The managed device monitors for the reset indicator being written to a specified location in FRU memory. Upon detecting the reset indicator in FRU memory, the managed device resets a bus controller coupled to the device management bus and transmits a reset notification on the device management bus. The remote access controller may include an I2C shim that controls access to an I2C multiplexer utilized for transmitting I2C commands from a service processor and an I2C coprocessor, preventing certain inoperable bus states due to concurrent operation of the I2C multiplexer by the I2C coprocessor and the service processor.

Abstract: Embodiments are described for detecting and recovering from an inoperable device management bus. A remote management controller is configured to offload device management bus transactions that use a messaging protocol. The messing protocol transactions are offloaded to a bus protocol controller that is responsible for managing bus operations using the messaging protocol. The bus protocol controller updates a set of bus status counters stored in a shared memory based on the processing of the offloaded messaging protocol transactions. The remote management controller processes device management bus transactions that use a bus protocol and updates the bus status counters based on the status of the bus protocol transactions. The remote management controller determines the status of the device management bus based on the bus status counters in shared memory, if the device management bus is inoperable, resets the remote management controller.

Abstract: Embodiments are described for operating a device management bus coupled to a remote access controller and a managed device. The remote access controller detects an inoperable state of the bus and determines a FRU (Field Replaceable Unit) memory is accessible on the managed device. A predefined reset indicator is written to the FRU memory. The managed device monitors for the reset indicator being written to a specified location in FRU memory. Upon detecting the reset indicator in FRU memory, the managed device resets a bus controller coupled to the device management bus and transmits a reset notification on the device management bus. The remote access controller may include an I2C shim that controls access to an I2C multiplexer utilized for transmitting I2C commands from a service processor and an I2C coprocessor, preventing certain inoperable bus states due to concurrent operation of the I2C multiplexer by the I2C coprocessor and the service processor.