[PATCH] arm: amlogic: add setbrg op to serial device

[Neil Armstrong]

On 23/09/2022 10:23, Neil Armstrong via groups.io wrote:
> Hi,
> 
> On 22/09/2022 20:51, Edoardo Tomelleri wrote:
>> Hello,
>> Il giorno gio 22 set 2022 alle ore 18:51 Neil Armstrong
>> <neil.armstrong at linaro.org> ha scritto:
>>>
>>> Hi,
>>>
>>> Sorry for the delay...
>> No problem, don't worry
>>
>>> Looks good !
>>>
>>> If someone can test it ? otherwise I'll take it for next release.
>> ...does it count if I've tested it? I have a radxa zero board (S905Y2
>> chip), this started as an experimentation
>> with editing register values in memory "for fun" and I decided to try
>> to make a patch out of it.
> 
> Yes it's perfect, thanks a lot for the test results !
> 
>> I do not have an oscilloscope so I can not accurately measure the baud
>> rate, but the logic is the same as
>> in linux and using an USB to UART (PL2303) adapter console input and
>> loady command work fine.
>> I've just repeated a small test: I'm using picocom and lrzsz in ymodem
>> mode under WSL, the usb adapter
>> is forwarded to WSL using usbip, but this should not change anything
>> at this kind of speed (I hope).
>> Here are some results sending a 1 MB test file (created once from /dev/urandom):
>> picocom v3.1
>>
>> port is        : /dev/ttyUSB0
>> flowcontrol    : none
>> baudrate is    : 115200
>> parity is      : none
>> databits are   : 8
>> stopbits are   : 1
>> [...]
>> send_cmd is    : sz --ymodem -vv
>> receive_cmd is : rz -vv -E
>> [...]
>> @115200
>> Bytes Sent:1048576   BPS:7762
>> @230400
>> Bytes Sent:1048576   BPS:16372
>> @460800
>> Bytes Sent:1048576   BPS:26681
>> @500000
>> Bytes Sent:1048576   BPS:27689
>> @500000 (2nd run)
>> Bytes Sent:1048576   BPS:27207
>>
>> At this point I stopped testing, I think my adapter is not good enough
>> and that the logic
>> is correct (I've read amlogic's public datasheets [1], but I've not
>> found a formula specified there),
>> Reading address (for hardware device UARTAO1, that _of course_ is not
>> listed there)
>> md.l 0xff803014 1
>> ff803014: 0180000f
>> This corresponds to REG5 of device UARTAO1, with bits 24 (USE_XTAL_CLK), 23
>> (use new baud rate) set, and bits 27 and 26 clear (so 24 MHz crystal
>> clock is divided by 3),
>> NEW_BAUD_RATE is f, so baud rate should be (8 MHz / (15 + 1)) = 500K.
>>
>> Other than that, I noticed that setting the env variable baudrate is
>> restricted to values allowed
>> in a compile time config, loady is not and loady ignores the return
>> value of meson_serial_setbrg
>> (it returns -EINVAL if for example a baudrate higher than 8'000'000 is
>> requested), here's a test
>> (with env variable baudrate=500000):
>> => loady 0x01000000 8000001
>> ## Switch baudrate to 8000001 bps and press ENTER ...
>> ## Ready for binary (ymodem) download to 0x01000000 at 8000001 bps...
>> C
>> *** file: ./dest
>> $ sz --ymodem -vv ./dest
>> Sending: dest
>> Bytes Sent:1048576   BPS:27781
>> Sending:
>> Ymodem sectors/kbytes sent:   0/ 0k
>> Transfer complete
>>
>> *** exit status: 0 ***
>> ## Total Size      = 0x00100000 = 1048576 Bytes
>> ## Start Addr      = 0x01000000
>> ## Switch baudrate to 500000 bps and press ESC ...
>> =>
>>
>> setbrg fails, the baud rate register is left at the 500'000 setting
>> and that's it.
>> I think the "for fun" experiment has gone a bit too far.
>>
>> Edoardo
>> [1] https://dl.radxa.com/zero/docs/hw/IO%20Interface%ef%bc%8dS905Y2%20Datasheet.pdf
> 
> I'll apply it then.
> 
> Acked-by: Neil Armstrong <narmstrong at baylibre.com>

Oops :
Acked-by: Neil Armstrong <neil.armstrong at linaro.org>

> 
> Please send more patches with such quality !
> 
> Thanks,
> Neil
> 
> 
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