Re: [PATCH] spi: Fixed division by zero warning

[Pratyush Yadav <p.yadav@xxxxxx>]

Hi Yoshitaka,

On 08/09/21 05:29AM, Yoshitaka Ikeda wrote:
> The reason for dividing by zero is because the dummy bus width is zero,
> but if the dummy n bytes is zero, it indicates that there is no data transfer,
> so there is no need for calculation.
> 
> Fixes: 7512eaf54190 ("spi: cadence-quadspi: Fix dummy cycle calculation when buswidth > 1")

You are right, there is no need for this.

> Signed-off-by: Yoshitaka Ikeda <ikeda@xxxxxxxxxxxx>
> ---
>  drivers/spi/atmel-quadspi.c  | 2 +-
>  drivers/spi/spi-bcm-qspi.c   | 3 ++-
>  drivers/spi/spi-mtk-nor.c    | 2 +-
>  drivers/spi/spi-stm32-qspi.c | 2 +-
>  4 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
> index 95d4fa32c299..92d9610df1fd 100644
> --- a/drivers/spi/atmel-quadspi.c
> +++ b/drivers/spi/atmel-quadspi.c
> @@ -310,7 +310,7 @@ static int atmel_qspi_set_cfg(struct atmel_qspi *aq,
>  		return mode;
>  	ifr |= atmel_qspi_modes[mode].config;
>  
> -	if (op->dummy.buswidth && op->dummy.nbytes)
> +	if (op->dummy.nbytes)
>  		dummy_cycles = op->dummy.nbytes * 8 / op->dummy.buswidth;
>  
>  	/*
> diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c
> index a78e56f566dd..0d95fe54b3c0 100644
> --- a/drivers/spi/spi-bcm-qspi.c
> +++ b/drivers/spi/spi-bcm-qspi.c
> @@ -395,7 +395,8 @@ static int bcm_qspi_bspi_set_flex_mode(struct bcm_qspi *qspi,
>  	if (addrlen == BSPI_ADDRLEN_4BYTES)
>  		bpp = BSPI_BPP_ADDR_SELECT_MASK;
>  
> -	bpp |= (op->dummy.nbytes * 8) / op->dummy.buswidth;
> +	if (op->dummy.nbytes)
> +		bpp |= (op->dummy.nbytes * 8) / op->dummy.buswidth;

This is a legitimate fix. The other 3 won't make much of a difference in 
practice but are good changes regardless IMO.

Acked-by: Pratyush Yadav <p.yadav@xxxxxx>

>  
>  	switch (width) {
>  	case SPI_NBITS_SINGLE:
> diff --git a/drivers/spi/spi-mtk-nor.c b/drivers/spi/spi-mtk-nor.c
> index 41e7b341d261..5c93730615f8 100644
> --- a/drivers/spi/spi-mtk-nor.c
> +++ b/drivers/spi/spi-mtk-nor.c
> @@ -160,7 +160,7 @@ static bool mtk_nor_match_read(const struct spi_mem_op *op)
>  {
>  	int dummy = 0;
>  
> -	if (op->dummy.buswidth)
> +	if (op->dummy.nbytes)
>  		dummy = op->dummy.nbytes * BITS_PER_BYTE / op->dummy.buswidth;
>  
>  	if ((op->data.buswidth == 2) || (op->data.buswidth == 4)) {
> diff --git a/drivers/spi/spi-stm32-qspi.c b/drivers/spi/spi-stm32-qspi.c
> index 27f35aa2d746..514337c86d2c 100644
> --- a/drivers/spi/spi-stm32-qspi.c
> +++ b/drivers/spi/spi-stm32-qspi.c
> @@ -397,7 +397,7 @@ static int stm32_qspi_send(struct spi_mem *mem, const struct spi_mem_op *op)
>  		ccr |= FIELD_PREP(CCR_ADSIZE_MASK, op->addr.nbytes - 1);
>  	}
>  
> -	if (op->dummy.buswidth && op->dummy.nbytes)
> +	if (op->dummy.nbytes)
>  		ccr |= FIELD_PREP(CCR_DCYC_MASK,
>  				  op->dummy.nbytes * 8 / op->dummy.buswidth);
>  
> -- 
> 2.33.0

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.