This is a modified version from Andre Przywara's patch series https://lore.kernel.org/patchwork/cover/812997/. [1] is a draft implementation of i.MX8MM SCMI ATF implementation that use smc as mailbox, power/clk is included, but only part of clk has been implemented to work with hardware, power domain only supports get name for now. The traditional Linux mailbox mechanism uses some kind of dedicated hardware IP to signal a condition to some other processing unit, typically a dedicated management processor. This mailbox feature is used for instance by the SCMI protocol to signal a request for some action to be taken by the management processor. However some SoCs does not have a dedicated management core to provide those services. In order to service TEE and to avoid linux shutdown power and clock that used by TEE, need let firmware to handle power and clock, the firmware here is ARM Trusted Firmware that could also run SCMI service. The existing SCMI implementation uses a rather flexible shared memory region to communicate commands and their parameters, it still requires a mailbox to actually trigger the action. This patch series provides a Linux mailbox compatible service which uses smc calls to invoke firmware code, for instance taking care of SCMI requests. The actual requests are still communicated using the standard SCMI way of shared memory regions, but a dedicated mailbox hardware IP can be replaced via this new driver. This simple driver uses the architected SMC calling convention to trigger firmware services, also allows for using "HVC" calls to call into hypervisors or firmware layers running in the EL2 exception level. Patch 1 contains the device tree binding documentation, patch 2 introduces the actual mailbox driver. Please note that this driver just provides a generic mailbox mechanism, though this is synchronous and one-way only (triggered by the OS only, without providing an asynchronous way of triggering request from the firmware). And while providing SCMI services was the reason for this exercise, this driver is in no way bound to this use case, but can be used generically where the OS wants to signal a mailbox condition to firmware or a hypervisor. Also the driver is in no way meant to replace any existing firmware interface, but actually to complement existing interfaces. [1] https://github.com/MrVan/arm-trusted-firmware/tree/scmi Peng Fan (2): DT: mailbox: add binding doc for the ARM SMC mailbox mailbox: introduce ARM SMC based mailbox .../devicetree/bindings/mailbox/arm-smc.txt | 96 +++++++++++++ drivers/mailbox/Kconfig | 7 + drivers/mailbox/Makefile | 2 + drivers/mailbox/arm-smc-mailbox.c | 154 +++++++++++++++++++++ include/linux/mailbox/arm-smc-mailbox.h | 10 ++ 5 files changed, 269 insertions(+) create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.txt create mode 100644 drivers/mailbox/arm-smc-mailbox.c create mode 100644 include/linux/mailbox/arm-smc-mailbox.h -- 2.16.4
