Before reset dbgu transmitter, we just wait TXEMPTY to drain the transmitter register. If not doing this, we may sometimes see several weird characters from DBGU.
A short delay is also added to make sure the new serial settings are settled.
Signed-off-by: Hong Xu hong.xu@atmel.com --- Change since V1: - Fix comment for easy reading
drivers/serial/atmel_usart.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/drivers/serial/atmel_usart.c b/drivers/serial/atmel_usart.c index e326b2b..6f9c2de 100644 --- a/drivers/serial/atmel_usart.c +++ b/drivers/serial/atmel_usart.c @@ -49,17 +49,23 @@ int serial_init(void) { atmel_usart3_t *usart = (atmel_usart3_t *)CONFIG_USART_BASE;
+ /* Just in case: drain transmitter register */ + while (!(readl(&usart->csr) & USART3_BIT(TXEMPTY))) + ; + writel(USART3_BIT(RSTRX) | USART3_BIT(RSTTX), &usart->cr);
serial_setbrg();
- writel(USART3_BIT(RXEN) | USART3_BIT(TXEN), &usart->cr); writel((USART3_BF(USART_MODE, USART3_USART_MODE_NORMAL) | USART3_BF(USCLKS, USART3_USCLKS_MCK) | USART3_BF(CHRL, USART3_CHRL_8) | USART3_BF(PAR, USART3_PAR_NONE) | USART3_BF(NBSTOP, USART3_NBSTOP_1)), &usart->mr); + writel(USART3_BIT(RXEN) | USART3_BIT(TXEN), &usart->cr); + /* 100us is enough for the new settings to be settled */ + __udelay(100);
return 0; }