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Date: Fri, 16 Dec 2022 23:23:59 +0100 From: Pali Rohár <pali@...nel.org> To: Segher Boessenkool <segher@...nel.crashing.org> Cc: Christophe Leroy <christophe.leroy@...roup.eu>, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, Nicholas Piggin <npiggin@...il.com> Subject: Re: [PATCH v1] powerpc/64: Set default CPU in Kconfig On Friday 16 December 2022 13:15:43 Segher Boessenkool wrote: > > Anyway, do you know what is e500mc64 core? I was trying to find some > > information about it, but it looks like some unreleased freescale core > > which predates e5500 core. > > It looks that way yes. It was submitted at > <https://gcc.gnu.org/pipermail/gcc-patches/2009-November/273251.html> > and committed as <https://gcc.gnu.org/g:b17f98b1c541>. It looks as if > it was based on the e500mc core, while e5500 is a new core (or > significantly different anyway). Just a two old Freescale PDF files which I found and mention e500mc-64: https://web.archive.org/web/20121215191707/http://www.freescale.com/files/ftf_2010/Americas/FTF10_ENT_F0453.pdf https://web.archive.org/web/20120905164305/http://www.freescale.com/files/ftf_2010/Americas/FTF10_ENT_F0273.pdf On page 6 in both documents is described P5020 with e500mc-64 cores. But production version of P5020 contains e5500 cores. Some other documents are also on nxp.com website: https://www.google.com/search?q=%22e500mc-64%22+site%3Anxp.com https://www.nxp.com/files-static/training/doc/MULTICORE_MORE.pdf https://www.nxp.com/docs/en/supporting-information/WBNR_FTF10_NET_F0707.pdf https://www.nxp.com/docs/en/supporting-information/WBNR_FTF10_NET_F0704.pdf > > ISA (without extensions like altivec) seems > > to be same for e500mc64, e5500 and e6500 cores and difference is only > > pipeline definitions in gcc config files. So if my understanding is > > correct then kernel binary compiled with any of these -mcpu= flag should > > work on any of those cores. Just for mismatches core binary will not be > > optimized for speed. > > It appears the E500MC64 never made it outside of FSL, so it is best not > to use it at all, imo. Yes, it really makes sense to not use e500mc64 flag. Maybe gcc documentation could be updated to mention this fact?
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