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SubjectRe: [PATCH] mtd: spi-nor: clear Extended Address Reg on switch to 3-byte addressing.
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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.
>
> Signed-off-by: NeilBrown <neil@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 &&

I think this should be made winbond-specific, macronix flashes do not
suffer from this I think. Otherwise looks good.

> + 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

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