[PATCH] mtd: spinand: macronix: use scratch buffer for DMA operation

[PATCH] mtd: spinand: macronix: use scratch buffer for DMA operation

[Daniel Golle]

The mx35lf1ge4ab_get_eccsr() function uses an SPI DMA operation to
read the eccsr, hence the buffer should not be on stack. Since commit
380583227c0c7f ("spi: spi-mem: Add extra sanity checks on the op param")
the kernel emmits a warning and blocks such operations.

Use the scratch buffer to get eccsr instead of trying to directly read
into a stack-allocated variable.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 drivers/mtd/nand/spi/macronix.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/spi/macronix.c b/drivers/mtd/nand/spi/macronix.c
index dce835132a1e2..722a9738ba370 100644
--- a/drivers/mtd/nand/spi/macronix.c
+++ b/drivers/mtd/nand/spi/macronix.c
@@ -83,9 +83,10 @@ static int mx35lf1ge4ab_ecc_get_status(struct spinand_device *spinand,
 		 * in order to avoid forcing the wear-leveling layer to move
 		 * data around if it's not necessary.
 		 */
-		if (mx35lf1ge4ab_get_eccsr(spinand, &eccsr))
+		if (mx35lf1ge4ab_get_eccsr(spinand, spinand->scratchbuf))
 			return nanddev_get_ecc_conf(nand)->strength;
 
+		eccsr = *spinand->scratchbuf;
 		if (WARN_ON(eccsr > nanddev_get_ecc_conf(nand)->strength ||
 			    !eccsr))
 			return nanddev_get_ecc_conf(nand)->strength;
-- 
2.39.1

Re: [PATCH] mtd: spinand: macronix: use scratch buffer for DMA operation

[Dhruva Gole]

Hi Daniel,

On 19/01/23 09:15, Daniel Golle wrote:
> The mx35lf1ge4ab_get_eccsr() function uses an SPI DMA operation to
> read the eccsr, hence the buffer should not be on stack. Since commit
> 380583227c0c7f ("spi: spi-mem: Add extra sanity checks on the op param")
> the kernel emmits a warning and blocks such operations.

Good catch!

> 
> Use the scratch buffer to get eccsr instead of trying to directly read
> into a stack-allocated variable.
> 
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> ---

Reviewed-by: Dhruva Gole <d-gole@ti.com>

>   drivers/mtd/nand/spi/macronix.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/spi/macronix.c b/drivers/mtd/nand/spi/macronix.c
> index dce835132a1e2..722a9738ba370 100644
> --- a/drivers/mtd/nand/spi/macronix.c
> +++ b/drivers/mtd/nand/spi/macronix.c
> @@ -83,9 +83,10 @@ static int mx35lf1ge4ab_ecc_get_status(struct spinand_device *spinand,
>   		 * in order to avoid forcing the wear-leveling layer to move
>   		 * data around if it's not necessary.
>   		 */
> -		if (mx35lf1ge4ab_get_eccsr(spinand, &eccsr))
> +		if (mx35lf1ge4ab_get_eccsr(spinand, spinand->scratchbuf))
>   			return nanddev_get_ecc_conf(nand)->strength;
>   
> +		eccsr = *spinand->scratchbuf;
>   		if (WARN_ON(eccsr > nanddev_get_ecc_conf(nand)->strength ||
>   			    !eccsr))
>   			return nanddev_get_ecc_conf(nand)->strength;

-- 
Thanks and Regards,
Dhruva Gole

Re: [PATCH] mtd: spinand: macronix: use scratch buffer for DMA operation

[Miquel Raynal]

Hi Daniel,

daniel@makrotopia.org wrote on Thu, 19 Jan 2023 03:45:43 +0000:

> The mx35lf1ge4ab_get_eccsr() function uses an SPI DMA operation to
> read the eccsr, hence the buffer should not be on stack. Since commit
> 380583227c0c7f ("spi: spi-mem: Add extra sanity checks on the op param")
> the kernel emmits a warning and blocks such operations.
> 
> Use the scratch buffer to get eccsr instead of trying to directly read
> into a stack-allocated variable.
> 
> Signed-off-by: Daniel Golle <daniel@makrotopia.org>
> ---

Looks like my scripts did not properly sent the "applied" e-mail, so
here it is, I applied this patch to nand/next.

>  drivers/mtd/nand/spi/macronix.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/spi/macronix.c b/drivers/mtd/nand/spi/macronix.c
> index dce835132a1e2..722a9738ba370 100644
> --- a/drivers/mtd/nand/spi/macronix.c
> +++ b/drivers/mtd/nand/spi/macronix.c
> @@ -83,9 +83,10 @@ static int mx35lf1ge4ab_ecc_get_status(struct spinand_device *spinand,
>  		 * in order to avoid forcing the wear-leveling layer to move
>  		 * data around if it's not necessary.
>  		 */
> -		if (mx35lf1ge4ab_get_eccsr(spinand, &eccsr))
> +		if (mx35lf1ge4ab_get_eccsr(spinand, spinand->scratchbuf))
>  			return nanddev_get_ecc_conf(nand)->strength;
>  
> +		eccsr = *spinand->scratchbuf;
>  		if (WARN_ON(eccsr > nanddev_get_ecc_conf(nand)->strength ||
>  			    !eccsr))
>  			return nanddev_get_ecc_conf(nand)->strength;


Thanks,
Miquèl