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| author | Johan Hovold <jhovold@gmail.com> | 2013-12-29 19:23:15 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-01-03 21:31:48 +0100 |
| commit | 5d85045f4b082800beb384094fc67fa0d2096563 (patch) | |
| tree | be5bc0158329ff7035506a1c4c2c3d1a4b1457e3 /drivers/usb/serial | |
| parent | USB: pl2303: add helper function for direct baud-rate encoding (diff) | |
| download | linux-5d85045f4b082800beb384094fc67fa0d2096563.tar.xz linux-5d85045f4b082800beb384094fc67fa0d2096563.zip | |
USB: pl2303: use direct baud-rate encoding when possible
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@googlemail.com>, 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@googlemail.com>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/serial')
| -rw-r--r-- | drivers/usb/serial/pl2303.c | 21 |
1 files 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); |