From 5d85045f4b082800beb384094fc67fa0d2096563 Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Sun, 29 Dec 2013 19:23:15 +0100 Subject: [PATCH] USB: pl2303: use direct baud-rate encoding when possible MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 , 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 Signed-off-by: Johan Hovold Signed-off-by: Greg Kroah-Hartman --- 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 b4e72979def..28e598638e0 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); -- 2.41.0