From 1c16606aac8f03be80d9c38ada00fd03123e0dbe Mon Sep 17 00:00:00 2001
From: =?utf8?q?Patrik=20Dahlstr=C3=B6m?= <risca@dalakolonin.se>
Date: Sat, 21 Dec 2019 17:25:12 +0100
Subject: [PATCH] serial: ns16550: Use old baud rate divisor for flushing if
not given
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If baud_divisor is not set (i.e. == -1), we should use the baud divisor
already in use for flushing the xmit register. If we don't flush the
xmit register, then SPL will hang.
Signed-off-by: Patrik Dahlström <risca@dalakolonin.se>
---
drivers/serial/ns16550.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/serial/ns16550.c b/drivers/serial/ns16550.c
index a92d2b1de8..9851663dc5 100644
--- a/drivers/serial/ns16550.c
+++ b/drivers/serial/ns16550.c
@@ -171,6 +171,13 @@ void NS16550_init(NS16550_t com_port, int baud_divisor)
== UART_LSR_THRE) {
if (baud_divisor != -1)
NS16550_setbrg(com_port, baud_divisor);
+ else {
+ // Re-use old baud rate divisor to flush transmit reg.
+ const int dll = serial_in(&com_port->dll);
+ const int dlm = serial_in(&com_port->dlm);
+ const int divisor = dll | (dlm << 8);
+ NS16550_setbrg(com_port, divisor);
+ }
serial_out(0, &com_port->mdr1);
}
#endif
--
2.39.5