From: Ilpo Järvinen ilpo.jarvinen@linux.intel.com
commit 5c5f44e36217de5ead789ff25da71c31c2331c96 upstream.
The code lacks clearing of previous DEAT/DEDT values. Thus, changing values on the fly results in garbage delays tending towards the maximum value as more and more bits are ORed together. (Leaving RS485 mode would have cleared the old values though).
Fixes: 1bcda09d2910 ("serial: stm32: add support for RS485 hardware control mode") Cc: stable stable@kernel.org Signed-off-by: Ilpo Järvinen ilpo.jarvinen@linux.intel.com Link: https://lore.kernel.org/r/20220627150753.34510-1-ilpo.jarvinen@linux.intel.c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/stm32-usart.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c @@ -72,6 +72,8 @@ static void stm32_config_reg_rs485(u32 * *cr3 |= USART_CR3_DEM; over8 = *cr1 & USART_CR1_OVER8;
+ *cr1 &= ~(USART_CR1_DEDT_MASK | USART_CR1_DEAT_MASK); + if (over8) rs485_deat_dedt = delay_ADE * baud * 8; else