>-----Original Message----- >From: U-Boot <u-boot-boun...@lists.denx.de> On Behalf Of Rasmus Villemoes >Sent: Friday, September 18, 2020 1:51 PM >To: Stefan Roese <s...@denx.de>; u-boot@lists.denx.de >Cc: Christophe Leroy <christophe.le...@c-s.fr>; Wolfgang Denk ><w...@denx.de>; Simon Glass <s...@chromium.org>; Tom Rini ><tr...@konsulko.com> >Subject: Re: [PATCH] powerpc: reduce number of WATCHDOG_RESET calls >from flush_cache > >On 04/06/2020 12.31, Stefan Roese wrote: >> On 04.06.20 11:30, Rasmus Villemoes wrote: >>> Calling WATCHDOG_RESET for each and every cache line is overkill. >>> >>> In our case, the kernel image is a little over 7MB, and the almost >>> 500000 calls of WATCHDOG_RESET() adds about one second to the >>> boottime. >>> >>> I very highly doubt there's any real hardware where flushing 64K from >>> cache to memory takes more than a few milliseconds, so this should be >>> completely safe. Since it reduces the number of >>> WATCHDOG_RESET() calls by roughly a factor of 1000, the overhead from >>> those is practically eliminated. (Just in case the range flushed is >>> so small that it doesn't cross a 64K boundary, add a single >>> WATCHDOG_RESET() between the loops). >>> >>> 64K is chosen because that's also the default chunk size used by the >>> hashing algorithms, and when, say, a sha256 digest of a kernel image >>> of a few MB is being verified, that's almost guaranteed to be >>> cache-cold, so apart from the computations being done, the hashing is >>> also bounded by memory speed - so if 64K works for those cases, it >>> should certainly also work when memory access is the only thing being >done. >>> >>> Signed-off-by: Rasmus Villemoes <rasmus.villem...@prevas.dk> >> >> Reviewed-by: Stefan Roese <s...@denx.de> > <snip> Applied to u-boot-mpc85xx. Awaiting upstream
Thanks Priyanka
