Use direct baud-rate encoding rather than divisors for supported baud
rates.
This restores the way baud rates were set prior to commit 8d48fdf689fe
("USB: PL2303: correctly handle baudrates above 115200") which added
divisor encoding, but also switched to the new encoding method for all
baudrates above 115200.
As noted by Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx>, baud rate 500k
was later errounously added to the supported baud-rate table although
it can only be set using divisors.
Note that the current implementation could easily be extended to support
arbitrary non-standard baud rates using divisors (e.g. by falling back
to divisors when the table lookup fails).
Cc: Frank Schäfer <fschaefer.oss@xxxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
---
drivers/usb/serial/pl2303.c | 21 +++++++++++++--------
1 file changed, 13 insertions(+), 8 deletions(-)
diff --git a/drivers/usb/serial/pl2303.c b/drivers/usb/serial/pl2303.c
index b4e72979def7..28e598638e0a 100644
--- a/drivers/usb/serial/pl2303.c
+++ b/drivers/usb/serial/pl2303.c
@@ -312,14 +312,15 @@ static int pl2303_set_control_lines(struct usb_serial_port *port, u8 value)
}
/*
- * Returns the nearest supported baud rate.
+ * Returns the nearest supported baud rate that can be set directly without
+ * using divisors.
*/
static speed_t pl2303_get_supported_baud_rate(speed_t baud)
{
static const speed_t baud_sup[] = {
75, 150, 300, 600, 1200, 1800, 2400, 3600, 4800, 7200, 9600,
14400, 19200, 28800, 38400, 57600, 115200, 230400, 460800,
- 500000, 614400, 921600, 1228800, 2457600, 3000000, 6000000
+ 614400, 921600, 1228800, 2457600, 3000000, 6000000
};
unsigned i;
@@ -379,6 +380,7 @@ static void pl2303_encode_baud_rate(struct tty_struct *tty,
{
struct usb_serial *serial = port->serial;
struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
+ speed_t baud_sup;
speed_t baud;
baud = tty_get_baud_rate(tty);
@@ -388,14 +390,17 @@ static void pl2303_encode_baud_rate(struct tty_struct *tty,
if (spriv->type->max_baud_rate)
baud = min_t(speed_t, baud, spriv->type->max_baud_rate);
+ /*
+ * Set baud rate to nearest supported value.
+ *
+ * NOTE: Baud rate 500k can only be set using divisors.
+ */
+ baud_sup = pl2303_get_supported_baud_rate(baud);
- /* Set baud rate to nearest supported value. */
- baud = pl2303_get_supported_baud_rate(baud);
-
- if (baud <= 115200)
- baud = pl2303_encode_baud_rate_direct(buf, baud);
- else
+ if (baud == 500000)
baud = pl2303_encode_baud_rate_divisor(buf, baud);
+ else
+ baud = pl2303_encode_baud_rate_direct(buf, baud_sup);
/* Save resulting baud rate */
tty_encode_baud_rate(tty, baud, baud);
--
1.8.3.2
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