On 05/05/2020 23:01:19+0200, Rasmus Villemoes wrote: > Thanks for the quick replies, both. Unfortunately, being able to read BF > from linux is not relevant to us - all the handling happens early in the > bootloader (including clearing BF, so that we can detect that the > previous boot failed only because of power fail - hence whether the > linux driver clears BF or not is not relevant). We really just want > linux to not touch the bits in CTRL3 at all. >
Well, in that case, Linux doesn't touch the BF bit anymore unless userspace uses the ioctls so you should be ok using it from your bootloader. > Hm, wait. Re-reading the above suggests that BF can get set even if BTSE > is not, and a quick experiment shows that is true - I must have misread > the data sheet. While I think that's fine for now (currently I only > print the time of last switch-over as a diagnostic), I did have some use > case in mind for comparing that timestamp to the current time and make > decisions based on that. But until I figure out exactly what I want to > use it for, and until we actually upgrade to 5.4+, there's no rush. > Configuring the timestamps is something else I want to do but I still didn't finish to design the proper interface. It is definitively on the todo list. -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
