On Fri, Mar 12, 2021 at 08:17:55AM -0500, Michael G. Katzmann wrote:
> On 3/11/21 11:08 AM, Johan Hovold wrote:
> >> static speed_t pl2303_encode_baud_rate_divisor( struct usb_serial_port *port,
> >> unsigned char buf[4],
> >> speed_t baud)
> >> {
> >> unsigned int baseline, mantissa, exponent;
> >> struct usb_serial *serial = port->serial;
> >> struct pl2303_serial_private *spriv = usb_get_serial_data(serial);
> >>
> >> /*
> >> * Apparently the formula is:
> >> * baudrate = 12M * 32 / (mantissa * 4^exponent)
> >> * where
> >> * mantissa = buf[8:0]
> >> * exponent = buf[11:9]
> >> *
> >> * TA version has more precision
> >> * uses mantissa = buf[bits 10:0 ]
> > So you discovered that there were even more bits here? Your first
> > version used ten bits, I believe.
> >
> > I got an offline mail from a third person having problems with the TA
> > and who had also verified eleven bits here.
>
> I was basing this on Joe's discovery of the value used for 110 bd by
> the windows driver (confirmed by Charles). The sequence 80 01 a6 a8
> implies that the mantissa is 0x6a8 (i.e. 11 bits). The tests that I
> did seemed to confirm this.
Ah, of course.
> Pardon my ignorance of the process but where is the git repo for this
> development branch?
I'll wait for a few days before applying the series I posted yesterday
to the usb-next (development) branch, but I've pushed a pl2303-wip
branch for you that you can use use until then:
https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git/log/?h=pl2303-wip
You can fetch from
https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git
Johan
