From: Sean Nyekjaer sean@geanix.com
[ Upstream commit 62aa1a344b0904549f6de7af958e8a1136fd5228 ]
When this driver is used with a driver that uses preallocated spi_transfer structs. The speed_hz is halved by every run. This results in:
spi_stm32 44004000.spi: SPI transfer setup failed ads7846 spi0.0: SPI transfer failed: -22
Example when running with DIV_ROUND_UP(): - First run; speed_hz = 1000000, spi->clk_rate 125000000 div 125 -> mbrdiv = 7, cur_speed = 976562 - Second run; speed_hz = 976562 div 128,00007 (roundup to 129) -> mbrdiv = 8, cur_speed = 488281 - Third run; speed_hz = 488281 div 256,000131072067109 (roundup to 257) and then -EINVAL is returned.
Use DIV_ROUND_CLOSEST to allow to round down and allow us to keep the set speed.
Signed-off-by: Sean Nyekjaer sean@geanix.com Link: https://lore.kernel.org/r/20221103080043.3033414-1-sean@geanix.com Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spi-stm32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c index c8e546439fff..87502f39bc4f 100644 --- a/drivers/spi/spi-stm32.c +++ b/drivers/spi/spi-stm32.c @@ -255,7 +255,7 @@ static int stm32_spi_prepare_mbr(struct stm32_spi *spi, u32 speed_hz) u32 div, mbrdiv;
/* Ensure spi->clk_rate is even */ - div = DIV_ROUND_UP(spi->clk_rate & ~0x1, speed_hz); + div = DIV_ROUND_CLOSEST(spi->clk_rate & ~0x1, speed_hz);
/* * SPI framework set xfer->speed_hz to master->max_speed_hz if