On Mon, 2021-07-19 at 16:20 +0100, Mark Brown wrote: > On Fri, Jul 16, 2021 at 01:34:38PM -0500, Eddie James wrote: > > > Security changes in the SPI controller - in the device microcode. I > > can > > reword the commit if you like. > > How will people end up running this device microcode? Is this a bug > fix, or is this going to needlessly reduce performance for people > with > existing hardware? The hardware is still in development. As part of the development, the device microcode was changed to restrict transfers. The reason for this restriction was "security concerns". This restriction disallows the loop (or branch-if-not-equal-and-increment) sequencer command. It also does not allow the read (or shift in if you prefer) command to specify the number of bytes in the command itself. Rather, the number of bits to shift in must be specified in a separate control register. This effectively means that the controller cannot transfer more than 8 bytes at a time. Therefore I suppose this is effectively a bug fix. There will be no hardware available without these restrictions, so it is not a needless reduction in performance. Every system that can run this driver will run the more restrictive device microcode. Thanks, Eddie
