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| author | Sean Nyekjaer <sean@geanix.com> | 2022-11-03 09:00:42 +0100 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2022-11-03 13:25:40 +0000 |
| commit | 62aa1a344b0904549f6de7af958e8a1136fd5228 (patch) | |
| tree | a68c074add5c022530abbe55e1dbc322303dfeb0 /drivers/spi | |
| parent | 134af9aa88453aeb9224e407092530ebba366c6c (diff) | |
| download | lwn-62aa1a344b0904549f6de7af958e8a1136fd5228.tar.gz lwn-62aa1a344b0904549f6de7af958e8a1136fd5228.zip | |
spi: stm32: fix stm32_spi_prepare_mbr() that halves spi clk for every run
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>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi-stm32.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c index 3c2fa2e2f94a..def09cf0dc14 100644 --- a/drivers/spi/spi-stm32.c +++ b/drivers/spi/spi-stm32.c @@ -434,7 +434,7 @@ 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 |