diff mbox series

[F,2/2] USB: serial: pl2303: fix line-speed handling on newer chips

Message ID 20211022072217.468706-3-aaron.ma@canonical.com
State New
Headers show
Series USB: serial: pl2303: add support for PL2303HXN | expand

Commit Message

Aaron Ma Oct. 22, 2021, 7:22 a.m. UTC 
From: Johan Hovold <johan@kernel.org>

BugLink: https://bugs.launchpad.net/bugs/1948377

The latest chip family (HXN) apparently does not support setting the
line speed using divisors and instead needs to use the direct encoding
scheme for all rates.

This specifically enables 50, 110, 134, 200 bps and other rates not
supported by the original chip type.

Fixes: ebd09f1cd417 ("USB: serial: pl2303: add support for PL2303HXN")
Cc: stable@vger.kernel.org      # 5.5
Cc: Charles Yeh <charlesyeh522@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
(cherry picked from commit 979d9cbe75b922ab1695b8ad5576115774f72e62)
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
---
 drivers/usb/serial/pl2303.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index 25b4333e9f85..67d2249cae22 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -184,6 +184,7 @@  struct pl2303_type_data {
 	speed_t max_baud_rate;
 	unsigned long quirks;
 	unsigned int no_autoxonxoff:1;
+	unsigned int no_divisors:1;
 };
 
 struct pl2303_serial_private {
@@ -210,6 +211,7 @@  static const struct pl2303_type_data pl2303_type_data[TYPE_COUNT] = {
 	},
 	[TYPE_HXN] = {
 		.max_baud_rate		= 12000000,
+		.no_divisors		= true,
 	},
 };
 
@@ -572,8 +574,12 @@  static void pl2303_encode_baud_rate(struct tty_struct *tty,
 		baud = min_t(speed_t, baud, spriv->type->max_baud_rate);
 	/*
 	 * Use direct method for supported baud rates, otherwise use divisors.
+	 * Newer chip types do not support divisor encoding.
 	 */
-	baud_sup = pl2303_get_supported_baud_rate(baud);
+	if (spriv->type->no_divisors)
+		baud_sup = baud;
+	else
+		baud_sup = pl2303_get_supported_baud_rate(baud);
 
 	if (baud == baud_sup)
 		baud = pl2303_encode_baud_rate_direct(buf, baud);