serial: stm32: Clear prev values before setting RTS delays

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.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index bb2f6f02ce23bd45c66d6bb17e0132a11ef71057..d8e1b0356e33b176527f2f8aa2842bba5fc7cae6 100644 (file)
--- 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 *cr1, u32 *cr3, u32 delay_ADE,
        *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