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SubjectRe: [RFC PATCH 1/3] mtd: spi-nor: Introduce SNOR_F_IO_MODE_EN_VOLATILE
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On 9/29/20 3:29 PM, Tudor Ambarus wrote:
> We don't want to enter a stateful mode, where a X-X-X I/O mode
> is entered by setting a non-volatile bit, because in case of a
> reset or a crash, once in the non-volatile mode, we may not be able
> to recover in bootloaders and we may break the SPI NOR boot.
>
> Forbid by default the I/O modes that are set via a non-volatile bit.
>
> SPI_NOR_IO_MODE_EN_VOLATILE should be set just for the flashes that
> don't define the optional SFDP SCCR Map, so that we don't pollute the
> flash info flags.
>

I would make this SPI_NOR_IO_MODE_EN_NON_VOLATILE. Because flashes with
volatile bits to change IO modes are more common than non volatile ones
and above change makes its easier to spot such quirky flashes.

> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
> drivers/mtd/spi-nor/core.c | 6 ++++++
> drivers/mtd/spi-nor/core.h | 6 ++++++
> 2 files changed, 12 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 34edfcf33172..c149b318e2e8 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -3089,6 +3089,9 @@ static int spi_nor_octal_dtr_enable(struct spi_nor *nor, bool enable)
> nor->write_proto == SNOR_PROTO_8_8_8_DTR))
> return 0;
>
> + if (!(nor->flags & SNOR_F_IO_MODE_EN_VOLATILE))
> + return 0;
> +
> ret = nor->params->octal_dtr_enable(nor, enable);
> if (ret)
> return ret;
> @@ -3474,6 +3477,9 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
> if (info->flags & SPI_NOR_4B_OPCODES)
> nor->flags |= SNOR_F_4B_OPCODES;
>
> + if (info->flags & SPI_NOR_IO_MODE_EN_VOLATILE)
> + nor->flags |= SNOR_F_IO_MODE_EN_VOLATILE;
> +
> ret = spi_nor_set_addr_width(nor);
> if (ret)
> return ret;
> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> index 10dc03506f93..c2755c82f978 100644
> --- a/drivers/mtd/spi-nor/core.h
> +++ b/drivers/mtd/spi-nor/core.h
> @@ -27,6 +27,7 @@ enum spi_nor_option_flags {
> SNOR_F_HAS_4BIT_BP = BIT(12),
> SNOR_F_HAS_SR_BP3_BIT6 = BIT(13),
> SNOR_F_SOFT_RESET = BIT(14),
> + SNOR_F_IO_MODE_EN_VOLATILE = BIT(15),
> };
>
> struct spi_nor_read_command {
> @@ -323,6 +324,11 @@ struct flash_info {
> */
> #define SPI_NOR_OCTAL_DTR_READ BIT(19) /* Flash supports octal DTR Read. */
> #define SPI_NOR_OCTAL_DTR_PP BIT(20) /* Flash supports Octal DTR Page Program */
> +#define SPI_NOR_IO_MODE_EN_VOLATILE BIT(21) /*
> + * Flash enables the best
> + * available I/O mode via a
> + * volatile bit.
> + */
>
> /* Part specific fixup hooks. */
> const struct spi_nor_fixups *fixups;
>

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