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spi: stm32: FIFO threshold level - fix align packet size 

commit a590370d91 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: Roman Guskov <rguskov@dh-electronics.com>
Fixes: dcbe0d84df ("spi: add driver for STM32 SPI controller")
Reviewed-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20201221123532.27272-1-rguskov@dh-electronics.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Roman Guskov 2020-12-21 13:35:32 +01:00 committed by Greg Kroah-Hartman
parent 9ff4796e6f
commit 12e8bcaef6
1 changed files with 2 additions and 2 deletions
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4
drivers/spi/spi-stm32.c
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@ -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;