diff mbox series

mtd: spi-nor: core: replace dummy buswidth from addr to data

Message ID 20241107093016.151448-1-linchengming884@gmail.com
State New
Headers show
Series mtd: spi-nor: core: replace dummy buswidth from addr to data | expand

Commit Message

Cheng Ming Lin Nov. 7, 2024, 9:30 a.m. UTC 
From: Cheng Ming Lin <chengminglin@mxic.com.tw>

The default dummy cycle for Macronix SPI NOR flash in Octal Output
Read Mode(1-1-8) is 20.

Currently, the dummy buswidth is set according to the address bus width.
In the 1-1-8 mode, this means the dummy buswidth is 1. When converting
dummy cycles to bytes, this results in 20 x 1 / 8 = 2 bytes, causing the
host to read data 4 cycles too early.

Since the protocol data buswidth is always greater than or equal to the
address buswidth. Setting the dummy buswidth to match the data buswidth
increases the likelihood that the dummy cycle-to-byte conversion will be
divisible, preventing the host from reading data prematurely.

Signed-off-by: Cheng Ming Lin <chengminglin@mxic.com.tw>
---
 drivers/mtd/spi-nor/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Pratyush Yadav Nov. 7, 2024, 5 p.m. UTC | #1 
On Thu, Nov 07 2024, Cheng Ming Lin wrote:

> From: Cheng Ming Lin <chengminglin@mxic.com.tw>
>
> The default dummy cycle for Macronix SPI NOR flash in Octal Output
> Read Mode(1-1-8) is 20.
>
> Currently, the dummy buswidth is set according to the address bus width.
> In the 1-1-8 mode, this means the dummy buswidth is 1. When converting
> dummy cycles to bytes, this results in 20 x 1 / 8 = 2 bytes, causing the
> host to read data 4 cycles too early.
>
> Since the protocol data buswidth is always greater than or equal to the
> address buswidth. Setting the dummy buswidth to match the data buswidth
> increases the likelihood that the dummy cycle-to-byte conversion will be
> divisible, preventing the host from reading data prematurely.

Makes sense.

Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
diff mbox series

Patch

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index f9c189ed7353..c7aceaa8a43f 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -89,7 +89,7 @@  void spi_nor_spimem_setup_op(const struct spi_nor *nor,
 		op->addr.buswidth = spi_nor_get_protocol_addr_nbits(proto);
 
 	if (op->dummy.nbytes)
-		op->dummy.buswidth = spi_nor_get_protocol_addr_nbits(proto);
+		op->dummy.buswidth = spi_nor_get_protocol_data_nbits(proto);
 
 	if (op->data.nbytes)
 		op->data.buswidth = spi_nor_get_protocol_data_nbits(proto);