Messages in this thread | | | From | NeilBrown <> | Date | Sat, 21 Apr 2018 07:28:19 +1000 | Subject | Re: [PATCH v2] mtd: spi-nor: clear Winbond Extended Address Reg on switch to 3-byte addressing. |
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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. I chose Fixes: 59b356ffd0b0 ("mtd: m25p80: restore the status of SPI flash when exiting") as this patch it useless without that one.
I also fixed the comment and have resent.
Thanks, NeilBrown
> >> --- >> >> following a helpful discussion with Marek, I've revised the description >> a little, and make the code change specific to winbond. >> I've change the OP names to RDEAR and WREAR instead of RDXA and WRXA to >> match names used in the Macronix documentation. Winbond documentation >> doesn't provide abbreviated OP names. >> >> Thanks, >> NeilBrown >> >> >> drivers/mtd/spi-nor/spi-nor.c | 13 +++++++++++++ >> include/linux/mtd/spi-nor.h | 2 ++ >> 2 files changed, 15 insertions(+) >> >> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c >> index d445a4d3b770..0d0af0acf8b9 100644 >> --- a/drivers/mtd/spi-nor/spi-nor.c >> +++ b/drivers/mtd/spi-nor/spi-nor.c >> @@ -284,6 +284,19 @@ static inline int set_4byte(struct spi_nor *nor, const struct flash_info *info, >> if (need_wren) >> write_disable(nor); >> >> + if (!status && !enable && >> + JEDEC_MFR(info) == SNOR_MFR_WINBOND) { >> + /* On Winbond W25Q256FV, leaving 4byte mode causes > > We use regular kernel-comment style in MTD: > > /* > * blablabla > */ > > Thanks, > > Boris > >> + * the Extended Address Register to be set to 1, so all >> + * 3-byte-address reads come from the second 16M. >> + * We must clear the register to enable normal behavior. >> + */ >> + write_enable(nor); >> + nor->cmd_buf[0] = 0; >> + nor->write_reg(nor, SPINOR_OP_WREAR, nor->cmd_buf, 1); >> + write_disable(nor); >> + } >> + >> return status; >> default: >> /* Spansion style */ >> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h >> index de36969eb359..e60da0d34cc1 100644 >> --- a/include/linux/mtd/spi-nor.h >> +++ b/include/linux/mtd/spi-nor.h >> @@ -62,6 +62,8 @@ >> #define SPINOR_OP_RDCR 0x35 /* Read configuration register */ >> #define SPINOR_OP_RDFSR 0x70 /* Read flag status register */ >> #define SPINOR_OP_CLFSR 0x50 /* Clear flag status register */ >> +#define SPINOR_OP_RDEAR 0xc8 /* Read Extended Address Register */ >> +#define SPINOR_OP_WREAR 0xc5 /* Write Extended Address Register */ >> >> /* 4-byte address opcodes - used on Spansion and some Macronix flashes. */ >> #define SPINOR_OP_READ_4B 0x13 /* Read data bytes (low frequency) */ [unhandled content-type:application/pgp-signature] | |