On Wed, Apr 06, 2022 at 03:47:11PM -0400, Tom Rini wrote: > On Tue, Mar 29, 2022 at 04:16:53PM +0100, abdellatif.elkhl...@arm.com wrote: > > From: Abdellatif El Khlifi <abdellatif.elkhl...@arm.com> > > > > This patchset adds support for Arm FF-A (Arm Firmware Framework for Armv8-A > > v1.0). > > > > FF-A support is generic by design and can be used by any Arm platform. > > > > The features added are as follows: > > > > 1/ FF-A device driver > > 2/ armffa command > > 3/ FF-A Sandbox driver > > 4/ FF-A Sandbox test cases > > 5/ FF-A MM communication > > > > > > The suggested design sees FF-A as a data bus allowing data exchange with > > the firmware > > running under TrustZone HW (such as Optee). The same approach was followed > > in the > > FF-A driver in Linux kernel > > (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/arm_ffa/bus.c?h=v5.15#n211)) > > > > u-boot boards using FF-A can provide a device tree node in a > > <board>-u-boot.dtsi file. > > Since the node can not be hosted in Linux device tree, we suggest using > > u-boot device tree. > > Why can't the node be in the upstream tree? It should be, so that it > can be shared between all users. Especially since there's in-Linux > users? > > -- > Tom
Linux already has an FF-A bus driver and doesn't use a device tree node for FF-A. The Linux driver registers FF-A as a bus: int arm_ffa_bus_init(void) { return bus_register(&ffa_bus_type); } https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/arm_ffa/bus.c?h=v5.15#n211 So, there is no user for the node in Linux. That's why we suggest hosting the node in the u-boot device tree (a u-boot.dtsi file)