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Commit 9b5a7943 authored by Roman Guskov's avatar Roman Guskov Committed by Greg Kroah-Hartman
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spi: stm32: FIFO threshold level - fix align packet size 



commit a590370d918fc66c62df6620445791fbe840344a upstream.

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: default avatarRoman Guskov <rguskov@dh-electronics.com>
Fixes: dcbe0d84 ("spi: add driver for STM32 SPI controller")
Reviewed-by: default avatarMarek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20201221123532.27272-1-rguskov@dh-electronics.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8b471834

drivers/spi/spi-stm32.c

+2 −2
Original line number Diff line number Diff line
@@ -299,9 +299,9 @@ static u32 stm32_spi_prepare_fthlv(struct stm32_spi *spi) 


	/* 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;



	return fthlv;

}