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usb: pl2303: move the two baud rate encoding methods to separate func…
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…tions

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Frank Schäfer authored and Greg Kroah-Hartman committed Aug 12, 2013
1 parent b9208c7 commit e917ba0
Showing 1 changed file with 114 additions and 101 deletions.
215 changes: 114 additions & 101 deletions drivers/usb/serial/pl2303.c
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Original file line number Diff line number Diff line change
Expand Up @@ -269,115 +269,128 @@ static int pl2303_set_control_lines(struct usb_serial_port *port, u8 value)
return retval;
}

static int pl2303_baudrate_encode_direct(int baud, enum pl2303_type type,
u8 buf[4])
{
/*
* NOTE: Only the values defined in baud_sup are supported !
* => if unsupported values are set, the PL2303 seems to
* use 9600 baud (at least my PL2303X always does)
*/
const int baud_sup[] = { 75, 150, 300, 600, 1200, 1800, 2400, 3600,
4800, 7200, 9600, 14400, 19200, 28800, 38400,
57600, 115200, 230400, 460800, 614400, 921600,
1228800, 2457600, 3000000, 6000000 };
int i;

/* Set baudrate to nearest supported value */
for (i = 0; i < ARRAY_SIZE(baud_sup); ++i) {
if (baud_sup[i] > baud)
break;
}
if (i == ARRAY_SIZE(baud_sup))
baud = baud_sup[i - 1];
else if (i > 0 && (baud_sup[i] - baud) > (baud - baud_sup[i - 1]))
baud = baud_sup[i - 1];
else
baud = baud_sup[i];
/* type_0, type_1 only support up to 1228800 baud */
if (type != HX)
baud = min_t(int, baud, 1228800);
/* Direct (standard) baud rate encoding method */
put_unaligned_le32(baud, buf);

return baud;
}

static int pl2303_baudrate_encode_divisor(int baud, enum pl2303_type type,
u8 buf[4])
{
/*
* Divisor based baud rate encoding method
*
* NOTE: it's not clear if the type_0/1 chips support this method
*
* divisor = 12MHz * 32 / baudrate = 2^A * B
*
* with
*
* A = buf[1] & 0x0e
* B = buf[0] + (buf[1] & 0x01) << 8
*
* Special cases:
* => 8 < B < 16: device seems to work not properly
* => B <= 8: device uses the max. value B = 512 instead
*/
unsigned int A, B;

/* Respect the specified baud rate limits */
baud = max_t(int, baud, 75);
if (type == HX)
baud = min_t(int, baud, 6000000);
else
baud = min_t(int, baud, 1228800);
/* Determine factors A and B */
A = 0;
B = 12000000 * 32 / baud; /* 12MHz */
B <<= 1; /* Add one bit for rounding */
while (B > (512 << 1) && A <= 14) {
A += 2;
B >>= 2;
}
if (A > 14) { /* max. divisor = min. baudrate reached */
A = 14;
B = 512;
/* => ~45.78 baud */
} else {
B = (B + 1) >> 1; /* Round the last bit */
}
/* Handle special cases */
if (B == 512)
B = 0; /* also: 1 to 8 */
else if (B < 16)
/*
* NOTE: With the current algorithm this happens
* only for A=0 and means that the min. divisor
* (respectively: the max. baudrate) is reached.
*/
B = 16; /* => 24 MBaud */
/* Encode the baud rate */
buf[3] = 0x80; /* Select divisor encoding method */
buf[2] = 0;
buf[1] = (A & 0x0e); /* A */
buf[1] |= ((B & 0x100) >> 8); /* MSB of B */
buf[0] = B & 0xff; /* 8 LSBs of B */
/* Calculate the actual/resulting baud rate */
if (B <= 8)
B = 512;
baud = 12000000 * 32 / ((1 << A) * B);

return baud;
}

static void pl2303_encode_baudrate(struct tty_struct *tty,
struct usb_serial_port *port,
enum pl2303_type type,
u8 buf[4])
{
struct usb_serial *serial = port->serial;
struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
int baud;

baud = tty_get_baud_rate(tty);
dev_dbg(&port->dev, "baud requested = %d\n", baud);
if (!baud)
return;

if (spriv->type != HX || baud <= 115200) {
/*
* NOTE: Only the values defined in baud_sup are supported !
* => if unsupported values are set, the PL2303 seems to
* use 9600 baud (at least my PL2303X always does)
*/
const int baud_sup[] = { 75, 150, 300, 600, 1200, 1800, 2400,
3600, 4800, 7200, 9600, 14400, 19200,
28800, 38400, 57600, 115200, 230400,
460800, 614400, 921600, 1228800,
2457600, 3000000, 6000000 };
int i;

/* Set baudrate to nearest supported value */
for (i = 0; i < ARRAY_SIZE(baud_sup); ++i) {
if (baud_sup[i] > baud)
break;
}

if (i == ARRAY_SIZE(baud_sup))
baud = baud_sup[i - 1];
else if (i > 0
&& (baud_sup[i] - baud) > (baud - baud_sup[i - 1]))
baud = baud_sup[i - 1];
else
baud = baud_sup[i];

/* type_0, type_1 only support up to 1228800 baud */
if (spriv->type != HX)
baud = min_t(int, baud, 1228800);

/* Direct (standard) baud rate encoding method */
put_unaligned_le32(baud, buf);
} else {
/*
* Divisor based baud rate encoding method
*
* NOTE: it's not clear if the type_0/1 chips
* support this method
*
* divisor = 12MHz * 32 / baudrate = 2^A * B
*
* with
*
* A = buf[1] & 0x0e
* B = buf[0] + (buf[1] & 0x01) << 8
*
* Special cases:
* => 8 < B < 16: device seems to work not properly
* => B <= 8: device uses the max. value B = 512 instead
*/
unsigned int A, B;

/* Respect the specified baud rate limits */
baud = max_t(int, baud, 75);
if (spriv->type == HX)
baud = min_t(int, baud, 6000000);
else
baud = min_t(int, baud, 1228800);
/* Determine factors A and B */
A = 0;
B = 12000000 * 32 / baud; /* 12MHz */
B <<= 1; /* Add one bit for rounding */
while (B > (512 << 1) && A <= 14) {
A += 2;
B >>= 2;
}
if (A > 14) { /* max. divisor = min. baudrate reached */
A = 14;
B = 512;
/* => ~45.78 baud */
} else {
B = (B + 1) >> 1; /* Round the last bit */
}
/* Handle special cases */
if (B == 512)
B = 0; /* also: 1 to 8 */
else if (B < 16)
/*
* NOTE: With the current algorithm this happens
* only for A=0 and means that the min. divisor
* (respectively: the max. baudrate) is reached.
*/
B = 16; /* => 24 MBaud */
/* Encode the baud rate */
buf[3] = 0x80; /* Select divisor encoding method */
buf[2] = 0;
buf[1] = (A & 0x0e); /* A */
buf[1] |= ((B & 0x100) >> 8); /* MSB of B */
buf[0] = B & 0xff; /* 8 LSBs of B */
/* Calculate the actual/resulting baud rate */
if (B <= 8)
B = 512;
baud = 12000000 * 32 / ((1 << A) * B);
}

/*
* There are two methods for setting/encoding the baud rate
* 1) Direct method: encodes the baud rate value directly
* => supported by all chip types
* 2) Divisor based method: encodes a divisor to a base value (12MHz*32)
* => supported by HX chips (and likely not by type_0/1 chips)
*/
if (type != HX || baud <= 115200)
baud = pl2303_baudrate_encode_direct(baud, type, buf);
else
baud = pl2303_baudrate_encode_divisor(baud, type, buf);
/* Save resulting baud rate */
tty_encode_baud_rate(tty, baud, baud);
dev_dbg(&port->dev, "baud set = %d\n", baud);
Expand Down Expand Up @@ -434,8 +447,8 @@ static void pl2303_set_termios(struct tty_struct *tty,
dev_dbg(&port->dev, "data bits = %d\n", buf[6]);
}

/* For reference buf[0]:buf[3] baud rate value */
pl2303_encode_baudrate(tty, port, &buf[0]);
/* For reference: buf[0]:buf[3] baud rate value */
pl2303_encode_baudrate(tty, port, spriv->type, buf);

/* For reference buf[4]=0 is 1 stop bits */
/* For reference buf[4]=1 is 1.5 stop bits */
Expand Down

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