This is a note to let you know that I've just added the patch titled
spi: stm32: fix stm32_spi_prepare_mbr() that halves spi clk for every run
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
spi-stm32-fix-stm32_spi_prepare_mbr-that-halves-spi-.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f8e8311c96dcf5d08dd6bb7d54fca81bce837ee2
Author: Sean Nyekjaer <sean@xxxxxxxxxx>
Date: Thu Nov 3 09:00:42 2022 +0100
spi: stm32: fix stm32_spi_prepare_mbr() that halves spi clk for every run
[ 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@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221103080043.3033414-1-sean@xxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/spi/spi-stm32.c b/drivers/spi/spi-stm32.c
index 96a73f9e2677..3c6f201b5dd8 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
