Date: Wed, 12 Dec 2018 18:26:59 -0700 From: Warner Losh <imp@bsdimp.com> To: Juli Mallett <juli@northcloak.com> Cc: Mori Hiroki <yamori813@yahoo.co.jp>, "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org> Subject: Re: MIPS future... Message-ID: <CANCZdfoP5LnH5Za9=mQBzoSAb0ptgaS29BtoFiBsh3TfLP0AXA@mail.gmail.com> In-Reply-To: <CAGSiXYxtDH0MBHFwCGSXxjE-22JWdmFbkX8zK2j9FsTRqcVJZg@mail.gmail.com> References: <CANCZdfpK5mPDDgpJ5PVhXF7-MixSouW8mAKkWQcaRnmYW%2Bpy0g@mail.gmail.com> <CANCZdfq8PMDdnEnBeBsQ-evJph9Bf1P-gp3v3DYzeUWHV5FOAw@mail.gmail.com> <367298.45441.qm@web103901.mail.ssk.yahoo.co.jp> <CANCZdfrfiR8=hd2nZsh1kuH6t_nbrdk=VHESZ4nzW-ZH2WfO-g@mail.gmail.com> <CAGSiXYxtDH0MBHFwCGSXxjE-22JWdmFbkX8zK2j9FsTRqcVJZg@mail.gmail.com>
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On Wed, Dec 12, 2018 at 6:05 PM Juli Mallett <juli@northcloak.com> wrote: > On Wed, 12 Dec 2018 at 16:12, Warner Losh <imp@bsdimp.com> wrote: > >> On Wed, Dec 12, 2018 at 3:53 PM Mori Hiroki <yamori813@yahoo.co.jp> >> wrote: >> >> > >> > >> > Hi >> > >> > >> > ----- Original Message ----- >> > >From: Warner Losh <imp@bsdimp.com> >> > >To: "freebsd-mips@freebsd.org" <freebsd-mips@freebsd.org> >> > >Date: 2018/12/13, Thu 07:15 >> > >Subject: Re: MIPS future... >> > > >> > >On Wed, Dec 12, 2018 at 11:15 AM Warner Losh <imp@bsdimp.com> wrote: >> > > >> > >> OK. To be a good player in the FreeBSD ecosystem, we need to do a >> few >> > >> things. >> > >> >> > >> First, we need to implement atomic_swap_64. hps did this for mips64 >> and >> > >> committed it. He sent me some further patches for it that I need to >> > commit >> > >> when I get a change, maybe at the airport tonight. >> > >> >> > >> But this brings up a couple of issues I'd like to bring up. >> > >> >> > >> First, to implement atomic_swap_64 on mips-32 is hard. In that it's >> not >> > >> just the canonical ldd/sdd sequence because those aren't available >> > there. >> > >> We can do the standard trick of reading STATUS0, clearing IE, storing >> > it, >> > >> do the operation and then restoring STATUS0. This is efficient enough >> > for >> > >> the use in the kernel for the supported cores we have. >> > >> >> > >> With two exceptions. First is running 32-bit kernels on 64-bit >> hardware. >> > >> We deprecated that with Octeon because of the weird hacks we needed >> to >> > do >> > >> too make it work. I'd like to universally deprecate this. There's >> little >> > >> benefit and a real cost to doing this. I'd like to remove the >> SWARM_SMP, >> > >> XLP, and GXEMUL32 (or at least remove the smp option). >> > >> >> > >> But there's JZ4780. It's a legit mips32 + SMP. It's on Image >> Creator's >> > >> CI20. This was released in Nov 2014 with a refresh in March 2015. >> This >> > is a >> > >> dead-end product line (there's no new cores and none new that I can >> > find). >> > >> This was a RPi competitor, but it was slower, less capable and more >> > >> expensive so it's kinda rare now. I'd say we need to de-support this >> > >> device. I know of only one user, and he's not responded to my email. >> I >> > >> think 12 will have to be the last release we have this in. Today, the >> > only >> > >> affect is for some drivers that can't run on this platform, but the >> > writing >> > >> is on the wall. >> > >> >> > >> That brings me to my next question: SWARM. Can we kill SWARM >> entirely? >> > >> It's for the BCM1250 part, released in sometime before 2000. It was >> > super >> > >> popular because it was the reference for a ton of things that >> followed. >> > I >> > >> think it's run is over and we can remove it. I can find no users of >> it >> > in >> > >> the nyc dmesg database. Mine has been in a plastic bag since before >> my >> > sone >> > >> was born in 2006... So I'm thinking we can remove this platform. It >> was >> > on >> > >> the edge last time I did a GC in mips-land. >> > >> >> > >> And then there's the even larger question: how many people are still >> > using >> > >> mips32? It looks like a fair number, maybe, but I have no idea for >> > sure, so >> > >> if you do, please provide feedback on the platforms you are running >> > FreeBSD >> > >> 11 or newer on. >> > >> >> > > >> > >There's one last issue this brings up. When writing the above code, I >> > >discovered I could use the non-racy DI instruction. However, that was >> > >introduced with mips32r2. This was defined in 2002 and gear appeared in >> > the >> > >market 2004 or 2005. I believe that all supported SoCs have mips32r2. >> > SWARM >> > >doesn't, which is another reason to kill it: it's getting in the way >> and >> > >providing no benefit. Would anybody object to the minimum ISA being >> raised >> > >to mips32r2 for all 32-bit mips platforms? >> > > >> > >Warner >> > >_______________________________________________ >> > >freebsd-mips@freebsd.org mailing list >> > >https://lists.freebsd.org/mailman/listinfo/freebsd-mips >> > >To unsubscribe, send any mail to "freebsd-mips-unsubscribe@freebsd.org >> " >> > > >> > > >> > > >> > >> > mips32 is called by 4K >> > mips32r2 is called by 24K >> > > I would note that although MIPS (the company) pushed this naming for a > period in the '00s, it can be confusing, because the R4000 (which was > widely called R4K or sometimes even just 4K), which was the basis for a lot > of MIPS CPUs, is actually MIPS-III (or mips3 in modern parlance, but I'm > trapped in the '90s), and 64-bit rather than 32-bit. MIPS32, of course, is > actually MIPS-III narrowed to 32-bit, plus a little extra. This leads some > people to assume that MIPS32 came first, and then there were 64-bit CPUs, > but this is not so. MIPS-III was 64-bit, R4000 was 64-bit, as were R4400, > and all of the SGI CPUs and many third-party MIPS ISA CPUs of the late '90s. > > So I would slightly discourage use of the "4K" moniker and rather suggest > using the ISA names, even though those confuse people, too, as consistently > as possible, in a thread where bit-width, modernness, etc., are on the > table. > True enough, later in my reply. I should have said 'mips4kc' since that's the core name that implements the 'mips32' ISA. I agree this is just about as confusing a set of conflicting naming conventions that could exist. Warner > > In current FreeBSD mips support at 4K is Rakink RT2880 and Atheros >> > AR531x. Ralink RT3050 later and Newer Atheros is 24K or 74K. >> > >> >> OK. That's good to know. The AR531x boards generally are under-provisioned >> for memory, and somewhat slow. The RT2880 appears to be in the same class. >> I'd be quite surprised if anybody could do anything non-trivial with those >> boards. >> >> Also Broadcom BCM4712 and BCM5354 is 4K but it's still hangup. Last >> > Broadcom MIPS soc that is BCM4718 and BCM5357 is 74K. >> > >> >> So the older SENTRY5 chips, which weren't all that common, but which are >> definitely mips4k chips. They are only a little better than the AR531x >> chips. The newer BCM stuff still looks relevant. Thanks for the pointers. >> >> I have question. Can do generate 24K code by gcc 4.2.1 and binutils? >> > >> >> I think that adding the following to the config file >> makeoptions ARCH_FLAGS="-march=mips32r2" >> comes close. You may need too add -EL if it's little endian. >> >> The only other config file tagged MIPS4k is GXEMUL, which may have run its >> useful lifetime in FreeBSD as well. >> >> Warner >> >> P.S. I'll post a summary of the implications of mips32"r1" removal if >> there's any opposition. >> _______________________________________________ >> freebsd-mips@freebsd.org mailing list >> https://lists.freebsd.org/mailman/listinfo/freebsd-mips >> To unsubscribe, send any mail to "freebsd-mips-unsubscribe@freebsd.org" >> >
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