Am 03.07.2013 12:45, schrieb Johan Hovold:
> 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
Argh... uhm... yes, sorry for the noise. :D
I've read these lines, but apparently I suffered from a total blackout
in the middle of this statement...
Great patch ! :D
Frank
>
>>> +
>>> + /* 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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