[Linux-stm32] [PATCH] spi: stm32: FIFO threshold level - fix align packet size

[Marek Vasut]

On 12/21/20 1:35 PM, Roman Guskov wrote:
> if cur_bpw <= 8 and xfer_len < 4 then the value of fthlv will be 1 and
> SPI registers content may have been lost.
> 
> * If SPI data register is accessed as a 16-bit register and DSIZE <= 8bit,
>    better to select FTHLV = 2, 4, 6 etc
> 
> * If SPI data register is accessed as a 32-bit register and DSIZE > 8bit,
>    better to select FTHLV = 2, 4, 6 etc, while if DSIZE <= 8bit,
>    better to select FTHLV = 4, 8, 12 etc
> 
> Signed-off-by: Roman Guskov <rguskov at dh-electronics.com>

I think this should also have the following tag:

Fixes: dcbe0d84dfa5 ("spi: add driver for STM32 SPI controller")

> ---
>   drivers/spi/spi-stm32.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
> index 9d8ceb63f7db..417c40154477 100644
> --- a/drivers/spi/spi-stm32.c
> +++ b/drivers/spi/spi-stm32.c
> @@ -494,9 +494,9 @@ static u32 stm32h7_spi_prepare_fthlv(struct stm32_spi *spi, u32 xfer_len)
>   
>   	/* align packet size with data registers access */
>   	if (spi->cur_bpw > 8)
> -		fthlv -= (fthlv % 2); /* multiple of 2 */
> +		fthlv += (fthlv % 2) ? 1 : 0;
>   	else
> -		fthlv -= (fthlv % 4); /* multiple of 4 */
> +		fthlv += (fthlv % 4) ? (4 - (fthlv % 4)) : 0;
>   
>   	if (!fthlv)
>   		fthlv = 1;
> 

Reviewed-by: Marek Vasut <marex at denx.de>