On Tue, Jan 28, 2020 at 04:37:59PM +0100, Benjamin Gaignard wrote: > Bus firewall framework aims to provide a kernel API to set the configuration > of the harware blocks in charge of busses access control. > > Framework architecture is inspirated by pinctrl framework: > - a default configuration could be applied before bind the driver. > If a configuration could not be applied the driver is not bind > to avoid doing accesses on prohibited regions. > - configurations could be apllied dynamically by drivers. > - device node provides the bus firewall configurations. > > An example of bus firewall controller is STM32 ETZPC hardware block > which got 3 possible configurations: > - trust: hardware blocks are only accessible by software running on trust > zone (i.e op-tee firmware). > - non-secure: hardware blocks are accessible by non-secure software (i.e. > linux kernel). > - coprocessor: hardware blocks are only accessible by the coprocessor. > Up to 94 hardware blocks of the soc could be managed by ETZPC. > /me confused. Is ETZPC accessible from the non-secure kernel space to begin with ? If so, is it allowed to configure hardware blocks as secure or trusted ? I am failing to understand the overall design of a system with ETZPC controller. > At least two other hardware blocks can take benefits of this: > - ARM TZC-400: http://infocenter.arm.com/help/topic/com.arm.doc.100325_0001_02_en/arm_corelink_tzc400_trustzone_address_space_controller_trm_100325_0001_02_en.pdf > which is able to manage up to 8 regions in address space. I strongly have to disagree with the above and NACK any patch trying to do so. AFAIK, no system designed has TZC with non-secure access. So we simply can't access this in the kernel and hence need no driver for the same. Please avoid adding above misleading information in future. -- Regards, Sudeep
