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SubjectRe: [PATCH v14 07/15] mtd: spi-nor: core: do 2 byte reads for SR and FSR in DTR mode
Date
On 9/30/20 9:57 PM, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> 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
> DTR mode, and then discard the second byte.
>
> Signed-off-by: Pratyush Yadav <p.yadav@ti.com>

Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.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 1465cf80f978..73a26e7e32c2 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -370,7 +370,7 @@ 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.
> */
> @@ -388,6 +388,11 @@ static int spi_nor_read_sr(struct spi_nor *nor, u8 *sr)
> if (nor->reg_proto == SNOR_PROTO_8_8_8_DTR) {
> 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);
> @@ -408,7 +413,8 @@ 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.
> */
> @@ -426,6 +432,11 @@ static int spi_nor_read_fsr(struct spi_nor *nor, u8 *fsr)
> if (nor->reg_proto == SNOR_PROTO_8_8_8_DTR) {
> 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
>

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