Hi all,
Hi Greg,
Recently I did an update to Fintek's 8250 driver, allowing it to support
baud rates up to 921600. The chip supports 4 clock rates. I changed it's
interal base clock to 14.746 MHz. (See
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-next&id=fab8a02b73eb2a42c589f943c377143f04b2bb73)
I want to support rates like B500000 too. Would be easy to set the clock
to full 24MHz, but then there's no proper 16x-divisor for B460800
(divisor 3 would give 499200 instead of 460800 - not close enough).
The table below ist from a Fintek datasheet
(http://pdf1.alldatasheet.com/datasheet-pdf/view/459084/FINTEK/F81866A.html).
It gives a quick overview which baud rates are possible with different
clock speeds.
I thought about writing a custom set_termios that decides which clock
matches best for the requested baud rate and changes it dynamically.
1) is there anything like that already in kernel source code?
2) good idea in general to do this in set_termios?
3) do i need to convert fintek.c to a standalone driver? I have no idea
how to proper override set_termios otherwise...
4) make that dynamic-baud-thing more generic so other ttys can use it too?
Happy to hear your thoughts!
Thanks in advance,
Lukas
--------------------------------------------------------------------------------
BAUD RATES BY CLOCK / DIVISOR
Base clock: 23.961661341853 MHz
16x divisor
Pre-Divider 13 1.625 1.300 1
Clock 1.843 14.746 18.431 23.961
50 399 499 649 2308
75 599 749 974 1538
110 879 1,098 1,428 1049
135 1,078 1,347 1,752 855
150 1,198 1,498 1,947 769
299 2,394 2,992 3,890 385
600 4,800 6,000 7,800 192
1,200 9,600 12,000 15,600 96
1,800 14,400 18,000 23,400 64
1,986 15,890 19,862 25,821 58
2,400 19,200 23,999 31,200 48
3,600 28,800 35,999 46,800 32
4,800 38,400 47,999 62,400 24
7,200 57,600 71,998 93,600 16
9,600 76,800 95,997 124,800 12
19,200 153,600 191,995 249,601 6
38,400 307,201 383,990 499,201 3
57,600 460,801 575,985 748,802 2
115,200 921,602 1,151,969 1,497,604 1
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