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Each co-existing SE can have one or multiple exclusive +MUs, dedicated to itself. None of the MU is shared between two SEs. +Communication of the MU is realized using the Linux mailbox driver. + +NXP Secure Enclave(SE) Interface +-------------------------------- +Although MU(s) is/are not shared between SE(s). But for SoC like i.MX95 which has +multiple SE(s) like HSM, V2X-HSM, V2X-SHE; all the SE(s) and their interfaces 'se-if' +that is/are dedicated to a particular SE will be enumerated and provisioned using the +single compatible node("fsl,imx95-se"). + +Each 'se-if' comprise of twp layers: +- (C_DEV Layer) User-Space software-access interface. +- (Service Layer) OS-level software-access interface. + + +--------------------------------------------+ + | Character Device(C_DEV) | + | | + | +---------+ +---------+ +---------+ | + | | misc #1 | | misc #2 | ... | misc #n | | + | | dev | | dev | | dev | | + | +---------+ +---------+ +---------+ | + | +-------------------------+ | + | | Misc. Dev Synchr. Logic | | + | +-------------------------+ | + | | + +--------------------------------------------+ + + +--------------------------------------------+ + | Service Layer | + | | + | +-----------------------------+ | + | | Message Serialization Logic | | + | +-----------------------------+ | + | +---------------+ | + | | imx-mailbox | | + | | mailbox.c | | + | +---------------+ | + | | + +--------------------------------------------+ + +- service layer: + This layer is responsible for ensuring the communication protocol that is defined + for communication with firmware. + + FW Communication protocol ensures two things: + - Serializing the messages to be sent over an MU. + + - FW can handle one command message at a time. + +- c_dev: + This layer offers character device contexts, created as '/dev/_mux_chx'. + Using these multiple device contexts that are getting multiplexed over a single MU, + userspace application(s) can call fops like write/read to send the command message, + and read back the command response message to/from Firmware. + fops like read & write use the above defined service layer API(s) to communicate with + Firmware. + + Misc-device(/dev/_mux_chn) synchronization protocol: + + Non-Secure + Secure + | + | + +---------+ +-------------+ | + | se_fw.c +<---->+imx-mailbox.c| | + | | | mailbox.c +<-->+------+ +------+ + +---+-----+ +-------------+ | MU X +<-->+ ELE | + | +------+ +------+ + +----------------+ | + | | | + v v | + logical logical | + receiver waiter | + + + | + | | | + | | | + | +----+------+ | + | | | | + | | | | + device_ctx device_ctx device_ctx | + | + User 0 User 1 User Y | + +------+ +------+ +------+ | + |misc.c| |misc.c| |misc.c| | + kernel space +------+ +------+ +------+ | + | + +------------------------------------------------------ | + | | | | + userspace /dev/ele_muXch0 | | | + /dev/ele_muXch1 | | + /dev/ele_muXchY | + | + +When a user sends a command to the firmware, it registers its device_ctx +as waiter of a response from firmware. + +Enclave's Firmware owns the storage management, over Linux filesystem. +For this c_dev provisions a dedicated slave device called "receiver". + +.. kernel-doc:: drivers/firmware/imx/se_fw.c + :export: