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USB: PL2303: correctly handle baudrates above 115200

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PL2303: correctly handle baudrates above 115200

Signed-off-by: Michal Sroczynski <msroczyn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Michał Sroczyński 2011-07-05 21:53:35 +02:00 committed by Greg Kroah-Hartman
parent 35da41375c
commit 8d48fdf689
1 changed files with 22 additions and 4 deletions
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26
drivers/usb/serial/pl2303.c
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@ -342,10 +342,28 @@ static void pl2303_set_termios(struct tty_struct *tty,
baud = 6000000;
}
dbg("%s - baud set = %d", __func__, baud);
buf[0] = baud & 0xff;
buf[1] = (baud >> 8) & 0xff;
buf[2] = (baud >> 16) & 0xff;
buf[3] = (baud >> 24) & 0xff;
if (baud <= 115200) {
buf[0] = baud & 0xff;
buf[1] = (baud >> 8) & 0xff;
buf[2] = (baud >> 16) & 0xff;
buf[3] = (baud >> 24) & 0xff;
} else {
/* apparently the formula for higher speeds is:
* baudrate = 12M * 32 / (2^buf[1]) / buf[0]
*/
unsigned tmp = 12*1000*1000*32 / baud;
buf[3] = 0x80;
buf[2] = 0;
buf[1] = (tmp >= 256);
while (tmp >= 256) {
tmp >>= 2;
buf[1] <<= 1;
}
if (tmp > 256) {
tmp %= 256;
}
buf[0] = tmp;
}
}
/* For reference buf[4]=0 is 1 stop bits */