On Sat, 21 Apr 2018 08:54:40 +1000 NeilBrown <n...@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. > > Acked-by: Marek Vasut <marek.va...@gmail.com> > Signed-off-by: NeilBrown <n...@brown.name> Applied to spi-nor/next. Thanks, Boris > --- > > Changes since v3: > Removed Fixes/stable tags. Added Acked-by from Marek. > Changes sinc3 v2: > Fixed comment style. > > > drivers/mtd/spi-nor/spi-nor.c | 14 ++++++++++++++ > include/linux/mtd/spi-nor.h | 2 ++ > 2 files changed, 16 insertions(+) > > diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c > index 5bfa36e95f35..42ae9a1529bb 100644 > --- a/drivers/mtd/spi-nor/spi-nor.c > +++ b/drivers/mtd/spi-nor/spi-nor.c > @@ -284,6 +284,20 @@ 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 > + * 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) */