spi: designware_spi: Fix off-by-one for checking fifo depth
PATCH 1/1 spi: designware_spi: Fix off-by-one for checking fifo depth
The depth could be from 2 to 256 from HW spec, so fix off-by-one for checking fifo depth.
---
Hi,
I don't have this hardware handy, so please test it.
drivers/spi/designware_spi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/spi/designware_spi.c +1 -1
@@ -164,7 +164,7 @@ static void spi_hw_init(struct dw_spi_priv *priv)if (!priv->fifo_len) {u32 fifo; -for (fifo =2 ; fifo <=257 ; fifo++) { +for (fifo =2 ; fifo <=256 ; fifo++) {dw_writew (priv,DW_SPI_TXFLTR , fifo);if (fifo !=dw_readw (priv,DW_SPI_TXFLTR ))break ;
Signature · 1 line
1.9.1
PATCH 1/1 spi: designware_spi: Fix off-by-one for checking fifo depth
Hi Axel,
Quoted 15 lines · Axel Lin
The depth could be from 2 to 256 from HW spec, so fix off-by-one for checking fifo depth.
Signed-off-by Axel Lin <[email protected]>---
Hi,
I don't have this hardware handy, so please test it.drivers/spi/designware_spi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)drivers/spi/designware_spi.c +0
-0
drivers/spi/designware_spi.c static void spi_hw_init(struct dw_spi_priv *priv) · line 170
Quoted 8 lines
drivers/spi/designware_spi.c +1
-1@@ -164,7 +164,7 @@ static void spi_hw_init(struct dw_spi_priv *priv)if (!priv->fifo_len) {u32 fifo; -for (fifo =2 ; fifo <=257 ; fifo++) { +for (fifo =2 ; fifo <=256 ; fifo++) {dw_writew (priv,DW_SPI_TXFLTR , fifo);if (fifo !=dw_readw (priv,DW_SPI_TXFLTR ))break ;
Please note that this code was not written by myself but is based on the Linux kernel version. And from my current understanding, this code tries to detect the FIFO size. So this 257 being bigger than the max value of 256 is most likely correct. Also another 257 is a few lines below your code:
dws->fifo_len = (fifo == 257) ? 0 : fifo;
So I don't think that we need to change this here.
BTW: It might be better to send this patch (or a question about this 256 vs 257) to the SPI Linux mailing list. The maintainer there will have deeper knowledge about this issue.
Thanks,
Stefan
PATCH 1/1 spi: designware_spi: Fix off-by-one for checking fifo depth
2014-12-19 15:35 GMT+08:00 Stefan Roese <[email protected]>:
Quoted 36 lines
Hi Axel,
Quoted 17 lines · Axel Lin
The depth could be from 2 to 256 from HW spec, so fix off-by-one for checking
fifo depth.Signed-off-by Axel Lin <[email protected]>---
Hi,
I don't have this hardware handy, so please test it.drivers/spi/designware_spi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)drivers/spi/designware_spi.c +0
-0drivers/spi/designware_spi.c static void spi_hw_init(struct dw_spi_priv *priv) · line 170
Quoted 8 lines
drivers/spi/designware_spi.c +1
-1@@ -164,7 +164,7 @@ static void spi_hw_init(struct dw_spi_priv *priv)if (!priv->fifo_len) {u32 fifo; -for (fifo =2 ; fifo <=257 ; fifo++) { +for (fifo =2 ; fifo <=256 ; fifo++) {dw_writew (priv,DW_SPI_TXFLTR , fifo);if (fifo !=dw_readw (priv,DW_SPI_TXFLTR ))break ;Please note that this code was not written by myself but is based on the Linux kernel version. And from my current understanding, this code tries to detect the FIFO size. So this 257 being bigger than the max value of 256 is most likely correct. Also another 257 is a few lines below your code:
Quoted 1 line
dws->fifo_len = (fifo == 257) ? 0 : fifo;
hi Stefan,
After the for loop iteration with "no-match" case, the fifo variable will be 258 in original code. So above code won't catch such case.
Quoted 6 lines
So I don't think that we need to change this here.
BTW: It might be better to send this patch (or a question about this 256 vs
257) to the SPI Linux mailing list. The maintainer there will have deeper knowledge about this issue.
Well, I'll send similar patch for linux driver for review (in spi maillist). Thanks.