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Subject[86/89] USB: cp210x: clean up, refactor and document speed handling
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
From: Johan Hovold <jhovold@gmail.com>

commit e5990874e511d5bbca23b3396419480cb2ca0ee7 upstream.

Clean up and refactor speed handling.
Document baud rate handling for CP210{1,2,4,5,10}.
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Cc: Preston Fick <preston.fick@silabs.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/serial/cp210x.c | 69 +++++++++++++++++++++++++++++++++++---------
1 file changed, 56 insertions(+), 13 deletions(-)
--- a/drivers/usb/serial/cp210x.c
+++ b/drivers/usb/serial/cp210x.c
@@ -39,6 +39,8 @@ static void cp210x_get_termios(struct tt
struct usb_serial_port *port);
static void cp210x_get_termios_port(struct usb_serial_port *port,
unsigned int *cflagp, unsigned int *baudp);
+static void cp210x_change_speed(struct tty_struct *, struct usb_serial_port *,
+ struct ktermios *);
static void cp210x_set_termios(struct tty_struct *, struct usb_serial_port *,
struct ktermios*);
static int cp210x_tiocmget(struct tty_struct *);
@@ -572,11 +574,62 @@ static void cp210x_get_termios_port(stru
*cflagp = cflag;
}

+/*
+ * CP2101 supports the following baud rates:
+ *
+ * 300, 600, 1200, 1800, 2400, 4800, 7200, 9600, 14400, 19200, 28800,
+ * 38400, 56000, 57600, 115200, 128000, 230400, 460800, 921600
+ *
+ * CP2102 and CP2103 support the following additional rates:
+ *
+ * 4000, 16000, 51200, 64000, 76800, 153600, 250000, 256000, 500000,
+ * 576000
+ *
+ * The device will map a requested rate to a supported one, but the result
+ * of requests for rates greater than 1053257 is undefined (see AN205).
+ *
+ * CP2104, CP2105 and CP2110 support most rates up to 2M, 921k and 1M baud,
+ * respectively, with an error less than 1%. The actual rates are determined
+ * by
+ *
+ * div = round(freq / (2 x prescale x request))
+ * actual = freq / (2 x prescale x div)
+ *
+ * For CP2104 and CP2105 freq is 48Mhz and prescale is 4 for request <= 365bps
+ * or 1 otherwise.
+ * For CP2110 freq is 24Mhz and prescale is 4 for request <= 300bps or 1
+ * otherwise.
+ */
+static void cp210x_change_speed(struct tty_struct *tty,
+ struct usb_serial_port *port, struct ktermios *old_termios)
+{
+ u32 baud;
+
+ baud = tty->termios->c_ospeed;
+
+ /* This maps the requested rate to a rate valid on cp2102 or cp2103.
+ *
+ * NOTE: B0 is not implemented.
+ */
+ baud = cp210x_quantise_baudrate(baud);
+
+ dbg("%s - setting baud rate to %u", __func__, baud);
+ if (cp210x_set_config(port, CP210X_SET_BAUDRATE, &baud,
+ sizeof(baud))) {
+ dev_warn(&port->dev, "failed to set baud rate to %u\n", baud);
+ if (old_termios)
+ baud = old_termios->c_ospeed;
+ else
+ baud = 9600;
+ }
+
+ tty_encode_baud_rate(tty, baud, baud);
+}
+
static void cp210x_set_termios(struct tty_struct *tty,
struct usb_serial_port *port, struct ktermios *old_termios)
{
unsigned int cflag, old_cflag;
- u32 baud;
unsigned int bits;
unsigned int modem_ctl[4];

@@ -588,19 +641,9 @@ static void cp210x_set_termios(struct tt
tty->termios->c_cflag &= ~CMSPAR;
cflag = tty->termios->c_cflag;
old_cflag = old_termios->c_cflag;
- baud = cp210x_quantise_baudrate(tty_get_baud_rate(tty));

- /* If the baud rate is to be updated*/
- if (baud != tty_termios_baud_rate(old_termios) && baud != 0) {
- dbg("%s - Setting baud rate to %d baud", __func__,
- baud);
- if (cp210x_set_config(port, CP210X_SET_BAUDRATE, &baud, sizeof(baud))) {
- dbg("Baud rate requested not supported by device");
- baud = tty_termios_baud_rate(old_termios);
- }
- }
- /* Report back the resulting baud rate */
- tty_encode_baud_rate(tty, baud, baud);
+ if (tty->termios->c_ospeed != old_termios->c_ospeed)
+ cp210x_change_speed(tty, port, old_termios);

/* If the number of data bits is to be updated */
if ((cflag & CSIZE) != (old_cflag & CSIZE)) {



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