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| |
| libtx2bpmp |
| ========== |
| |
| This library contains drivers necessary to interface with the Boot and Power |
| Management Processor (BPMP) co-processor on the NVIDIA TX2. The BPMP is |
| responsible for handling boot and power management functions and also controls |
| a few other devices. These devices are the clock controller, and an I2C |
| channel. |
| |
| The child devices of the BPMP are managed by sending requests to the BPMP |
| module via inter-processor communication mechanisms which involve the Inter-VM |
| Communication (IVC) protocol, Hardware Synchronisation Primitives (HSP) device |
| module, and some shared memory. |
| |
| HSP |
| --- |
| |
| The HSP module offers a number of primitives that can be used to synchronise |
| state between the processor and the co-processors on the board. These include: |
| - Shared mailboxes, which are essentially small data transfer buffers |
| - Shared semaphores |
| - Arbitrated sempahores, which are essentially semaphores that also include |
| state to avoid busy waiting |
| - Doorbells, which are essentially signals |
| |
| The HSP driver in this library currently only supports the doorbell mechanisms. |
| This driver is mainly used only by the BPMP driver in this library, but it can |
| be used for other purposes as well. |
| |
| Doorbells can be setup with the CPU complex/CPU subsystem (CCPLEX), Sensor |
| Processing Engine (SPE), Safety Cluster Engine (SCE), and the Audio Processing |
| Engine (APE) device modules. To first setup a doorbell, `tx2_hsp_init()` needs |
| to be called first to initialise the HSP interfaces. Afterwards, the doorbells |
| can to the device modules can be rung or checked by calling |
| `tx2_hsp_doorbell_ring()` or `tx2_hsp_doorbell_check()` respectively with the |
| right doorbell ID. |
| |
| IVC |
| --- |
| |
| The IVC protocol is used to facilitate communication over a shared memory |
| channel between the processor and other remote entities. The protocol functions |
| similar to the producer-consumer pattern. The channel is split into fixed size |
| message buffers that can be pushed or popped from the channel when messages |
| need to be sent or received. |
