On 04/08/2018 09:04 AM, NeilBrown wrote: > > 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. > > This patch adds code to implement that recommendation. Without this, > my GNUBEE-PC1 will not successfully reboot, as the Extended Address > Register is left with a value of '1'. When the SOC attempts to read > (in 3-byte address mode) the boot loader, it reads from the wrong > location.
Your board is broken by design and does not implement proper reset logic for the SPI NOR chip, right ? That is, when the CPU resets, the SPI NOR is left in some random undefined state instead of being reset too, yes? Doesn't this chip support 4-byte addressing opcodes ? If so, we should use those and keep the chip in 3-byte addressing mode. Would that work? > Signed-off-by: NeilBrown <n...@brown.name> > --- > drivers/mtd/spi-nor/spi-nor.c | 10 ++++++++++ > include/linux/mtd/spi-nor.h | 2 ++ > 2 files changed, 12 insertions(+) > > diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c > index d445a4d3b770..c303bf0d2982 100644 > --- a/drivers/mtd/spi-nor/spi-nor.c > +++ b/drivers/mtd/spi-nor/spi-nor.c > @@ -269,6 +269,7 @@ static inline int set_4byte(struct spi_nor *nor, const > struct flash_info *info, > int status; > bool need_wren = false; > u8 cmd; > + u8 val; > > switch (JEDEC_MFR(info)) { > case SNOR_MFR_MICRON: > @@ -283,6 +284,15 @@ static inline int set_4byte(struct spi_nor *nor, const > struct flash_info *info, > status = nor->write_reg(nor, cmd, NULL, 0); > if (need_wren) > write_disable(nor); > + if (!status && !enable && > + nor->read_reg(nor, SPINOR_OP_RDXA, &val, 1) == 0 && > + val != 0) { > + /* need to reset the Extended Address Register */ > + write_enable(nor); > + val = 0; > + nor->write_reg(nor, SPINOR_OP_WRXA, &val, 1); > + write_disable(nor); > + } > > return status; > default: > diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h > index de36969eb359..42954419cfdf 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_RDXA 0xc8 /* Read Extended Address > Register */ > +#define SPINOR_OP_WRXA 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) */ > -- Best regards, Marek Vasut