Gabor Juhos
2dff8ad926
tty/serial/ar933x_uart: fix baud rate calculation ...
The UART of the AR933x SoC implements a fractional divisor
for generating the desired baud rate.
The current code uses a fixed value for the fractional
part of the divisor, and this leads to improperly
calculated baud rates:
baud scale step real baud diff
300 5207* 8192 17756 17456 5818.66%
600 2603* 8192 35511 34911 5818.50%
1200 1301* 8192 71023 69823 5818.58%
2400 650* 8192 11241 8841 368.37%
4800 324* 8192 22645 17845 371.77%
9600 161 8192 9645 45 0.46%
14400 107 8192 14468 68 0.47%
19200 80 8192 19290 90 0.46%
28800 53 8192 28935 135 0.46%
38400 39 8192 39063 663 1.72%
57600 26 8192 57870 270 0.46%
115200 12 8192 120192 4992 4.33%
230400 5 8192 260417 30017 13.02%
460800 2 8192 520833 60033 13.02%
921600 0 8192 1562500 640900 69.93%
After the patch, the integer and fractional parts of the
divisor will be calculated dynamically. This ensures that
the UART will use correct baud rates:
baud scale step real baud diff
300 6 11 300 0 0.00%
600 54 173 600 0 0.00%
1200 30 195 1200 0 0.00%
2400 30 390 2400 0 0.00%
4800 48 1233 4800 0 0.00%
9600 78 3976 9600 0 0.00%
14400 98 7474 14400 0 0.00%
19200 55 5637 19200 0 0.00%
28800 130 19780 28800 0 0.00%
38400 36 7449 38400 0 0.00%
57600 78 23857 57600 0 0.00%
115200 43 26575 115200 0 0.00%
230400 23 28991 230400 0 0.00%
460800 11 28991 460800 0 0.00%
921600 5 28991 921599 -1 0.00%
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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2dff8ad926