Messages in this thread | | | From | NeilBrown <> | Date | Sat, 21 Apr 2018 08:51:56 +1000 | Subject | Re: [PATCH v2] mtd: spi-nor: clear Winbond Extended Address Reg on switch to 3-byte addressing. |
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On Sat, Apr 21 2018, Boris Brezillon wrote:
> On Sat, 21 Apr 2018 07:28:19 +1000 > NeilBrown <neil@brown.name> wrote: > >> On Fri, Apr 20 2018, Boris Brezillon wrote: >> >> > Hi Neil, >> > >> > On Mon, 16 Apr 2018 09:42:30 +1000 >> > NeilBrown <neil@brown.name> wrote: >> > >> >> Winbond spi-nor flash 32MB and larger have an 'Extended Address >> >> Register' as one option for addressing beyond 16MB (Macronix >> >> has the same concept, Spansion has EXTADD bits in the Bank Address >> >> Register). >> >> >> >> According to section >> >> 8.2.7 Write Extended Address Register (C5h) >> >> >> >> of the Winbond W25Q256FV data sheet (256M-BIT SPI flash) >> >> >> >> The Extended Address Register is only effective when the device is >> >> in the 3-Byte Address Mode. When the device operates in the 4-Byte >> >> Address Mode (ADS=1), any command with address input of A31-A24 >> >> will replace the Extended Address Register values. It is >> >> recommended to check and update the Extended Address Register if >> >> necessary when the device is switched from 4-Byte to 3-Byte Address >> >> Mode. >> >> >> >> So the documentation suggests clearing the EAR after switching to >> >> 3-byte mode. Experimentation shows that the EAR is *always* one after >> >> the switch to 3-byte mode, so clearing the EAR is mandatory at >> >> shutdown for a subsequent 3-byte-addressed reboot to work. >> >> >> >> Note that some SOCs (e.g. MT7621) do not assert a reset line at normal >> >> reboot, so we cannot rely on hardware reset. The MT7621 does assert a >> >> reset line at watchdog-reset. >> >> >> >> Signed-off-by: NeilBrown <neil@brown.name> >> > >> > We should probably backport the fix. Can you add a Fixes and Cc-stable >> > tag? >> >> It's a bit weird having Fixes when this isn't a regression, but I guess >> it doesn't hurt. > > Well, I thought you wanted this patch to be backported to stable > releases, hence my suggestion. Of course it's not a regression, since > the bug is here from the beginning, but nonetheless it's fixing a bug.
I have not interest in this patch going to stable. I'll be perfectly happy once it lands upstream.
> >> I chose >> Fixes: 59b356ffd0b0 ("mtd: m25p80: restore the status of SPI flash when exiting") >> as this patch it useless without that one. > > Not sure that's how Fixes should be used. IIUC, it should point to the > first commit where the bug was introduced, so I guess it's 0aa87b7563f1 > ("mtd: m25p80: add support for the windbond w25q256 chip") in this case.
That does make a certain sort of sense, but if you tried applying this patch to that kernel, it wouldn't apply at all. So it is hard to say that it fixes anything there.
I think it is best to drop the fixes/stable tags. It isn't a regression, doesn't cause data corruption, doesn't make it possible to crash the kernel, so it isn't really "stable" material in my mind.
Thanks, NeilBrown
> > Now, if you want to restrict the kernel releases this patch should be > backported to, you can use the '# vX.Y+' suffix in your Cc-stable tag. > >> >> I also fixed the comment and have resent. > > Thanks. [unhandled content-type:application/pgp-signature] | |