On 9/16/20 3:44 PM, Pratyush Yadav wrote:
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> Some controllers, like the cadence qspi controller, have trouble reading
> only 1 byte in DTR mode. So, do 2 byte reads for SR and FSR commands in
did you get garbage when reading only one byte?
> DTR mode, and then discard the second byte.
>
> Signed-off-by: Pratyush Yadav <p.ya...@ti.com>
> ---
> drivers/mtd/spi-nor/core.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index 88c9e18067f4..87c568debf14 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -368,7 +368,7 @@ int spi_nor_write_disable(struct spi_nor *nor)
> * spi_nor_read_sr() - Read the Status Register.
> * @nor: pointer to 'struct spi_nor'.
> * @sr: pointer to a DMA-able buffer where the value of the
> - * Status Register will be written.
> + * Status Register will be written. Should be at least 2 bytes.
> *
> * Return: 0 on success, -errno otherwise.
> */
> @@ -386,6 +386,11 @@ static int spi_nor_read_sr(struct spi_nor *nor, u8 *sr)
> if (spi_nor_protocol_is_dtr(nor->reg_proto)) {
> op.addr.nbytes = nor->params->rdsr_addr_nbytes;
> op.dummy.nbytes = nor->params->rdsr_dummy;
> + /*
> + * We don't want to read only one byte in DTR mode.
> So,
> + * read 2 and then discard the second byte.
> + */
> + op.data.nbytes = 2;
just for octal dtr, but should be fine if you update the previous patch
> }
>
> spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
> @@ -405,7 +410,8 @@ static int spi_nor_read_sr(struct spi_nor *nor, u8 *sr)
> * spi_nor_read_fsr() - Read the Flag Status Register.
> * @nor: pointer to 'struct spi_nor'
> * @fsr: pointer to a DMA-able buffer where the value of the
> - * Flag Status Register will be written.
> + * Flag Status Register will be written. Should be at least 2
> + * bytes.
> *
> * Return: 0 on success, -errno otherwise.
> */
> @@ -423,6 +429,11 @@ static int spi_nor_read_fsr(struct spi_nor *nor, u8 *fsr)
> if (spi_nor_protocol_is_dtr(nor->reg_proto)) {
> op.addr.nbytes = nor->params->rdsr_addr_nbytes;
> op.dummy.nbytes = nor->params->rdsr_dummy;
> + /*
> + * We don't want to read only one byte in DTR mode.
> So,
> + * read 2 and then discard the second byte.
> + */
> + op.data.nbytes = 2;
> }
>
> spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
> --
> 2.28.0
>
