Date: Thu, 28 Jun 2018 17:28:20 -0600 From: Warner Losh <imp@bsdimp.com> To: Emmanuel Vadot <manu@bidouilliste.com> Cc: Adrian Chadd <adrian.chadd@gmail.com>, "freebsd-embedded@freebsd.org" <freebsd-embedded@freebsd.org> Subject: Re: Atheros AR93xx NAND support Message-ID: <CANCZdfrGAuJLy2WM9pp_0uzaBZCTCirOTSo_kn7JzmqpUmM3iA@mail.gmail.com> In-Reply-To: <20180629011042.6e72464d7fc3294d96dd093f@bidouilliste.com> References: <CAF-mK=Xpmi6OStLbosfdwW7KHL4XSPky_7JDZgEosYr3m709aQ@mail.gmail.com> <CAJ-Vmo=JQ-rgPEBOHKMigJB5Kt0QUFVWUKQAh99vvnNqFmoByw@mail.gmail.com> <CANCZdfpC2ExBPytm3dmeno%2B_ZX9nCWRUJb_zmu7TZGbbokc8AQ@mail.gmail.com> <20180629011042.6e72464d7fc3294d96dd093f@bidouilliste.com>
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On Thu, Jun 28, 2018 at 5:10 PM, Emmanuel Vadot <manu@bidouilliste.com> wrote: > On Thu, 28 Jun 2018 14:46:16 -0600 > Warner Losh <imp@bsdimp.com> wrote: > > > If you had good access to datasheets, plus errata, plus vendor support, > you > > might be able to get a quality implementation in 3-4 months time, which > > would include time to revamp our NAND system. It doesn't include time to > > revamp NANDFS, though, which would be another 2-3 months to get rock > solid. > > > > Warner > > I don't know the state of NAND in MIPS world but in the ARM world it's > clearly fading out. But I've always wondered if instead of NANDFS one > could do a geom_ftl (Flash Transision Layer) that will do all the nand > stuff and then we can use UFS on it ? That's logically appealing, but inefficient.The tables needed get kinda big and/or you have to do a lot of NAND I/O to get the mappings since you are hiding things from the UFS layer. NANDFS is a log filesystem, so it knows how about how to interact with the append store that's NAND. It was one of the biggest problems with Fusion I/O's driver: it had to keep this translation table in memory. It made crash recovery difficult. It created points of contention that limited performance. It could be done, but experience suggests caution... Warnerhome | help
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