On Tue, Jul 02, 2013 at 05:44:01PM +0200, Frank Schäfer wrote:
> > - /* NOTE: Only the values defined in baud_sup are supported !
> > + /*
> > + * 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)
> > */
> > baud = tty_get_baud_rate(tty);
> > dev_dbg(&port->dev, "baud requested = %d\n", baud);
> > - if (baud) {
> > - /* Set baudrate to nearest supported value */
> > - for (k=0; k<ARRAY_SIZE(baud_sup); k++) {
> > - if (baud_sup[k] / baud) {
> > - baud_ceil = baud_sup[k];
> > - if (k==0) {
> > - baud = baud_ceil;
> > - } else {
> > - baud_floor = baud_sup[k-1];
> > - if ((baud_ceil % baud)
> > - > (baud % baud_floor))
> > - baud = baud_floor;
> > - else
> > - baud = baud_ceil;
> > - }
> > - break;
> > - }
> > - }
> [...]
> > - if (baud > 1228800) {
> > - /* type_0, type_1 only support up to 1228800 baud */
> > - if (spriv->type != HX)
> > - baud = 1228800;
> > - else if (baud > 6000000)
> > - baud = 6000000;
> > - }
> > - dev_dbg(&port->dev, "baud set = %d\n", baud);
> > - 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;
> > - }
> > - buf[0] = tmp;
> > + if (!baud)
> > + return;
> > +
> > + /* Set baudrate to nearest supported value */
> > + for (i = 0; i < ARRAY_SIZE(baud_sup); ++i) {
> > + if (baud_sup[i] > baud)
> > + break;
> > + }
>
> This isn't just a clean-up.
> It actually changes the baud rate determination from "next nearest" to
> "round downwards".
> I really think the current behavior is preferred/better, so please keep
> the old code.
> For example: a selection of 14300 baud results in 9600 baud with this
> patch applied, while the next nearest supported baud rate is 14400 baud.
>
> The rest of this patch (and AFAICS also the other patches of this
> series) is fine.
Thanks for looking at the patch. However, you missed the next few
lines which are part of the clean up of the old implementation:
> > +
> > + 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];
You see? Here the closest baud rate is selected just like before, but
without the need for those crazy division and modulo operations.
Johan
> > +
> > + /* type_0, type_1 only support up to 1228800 baud */
> > + if (spriv->type != HX)
> > + baud = max_t(int, baud, 1228800);
> > +
> > + if (baud <= 115200) {
> > + put_unaligned_le32(baud, buf);
> > + } else {
> > + /*
> > + * Apparently the formula for higher speeds is:
> > + * baudrate = 12M * 32 / (2^buf[1]) / buf[0]
> > + */
> > + unsigned tmp = 12000000 * 32 / baud;
> > + buf[3] = 0x80;
> > + buf[2] = 0;
> > + buf[1] = (tmp >= 256);
> > + while (tmp >= 256) {
> > + tmp >>= 2;
> > + buf[1] <<= 1;
> > }
> > + buf[0] = tmp;
> > }
> >
> > /* Save resulting baud rate */
> > - if (baud)
> > - tty_encode_baud_rate(tty, baud, baud);
> > + tty_encode_baud_rate(tty, baud, baud);
> > + dev_dbg(&port->dev, "baud set = %d\n", baud);
> > }
> >
> > static void pl2303_set_termios(struct tty_struct *tty,
>
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