On 03/09/2015 07:27 AM, Måns Rullgård wrote:
> Mason <slash.tmp@xxxxxxx> writes:
>
>> On 09/03/2015 10:34, Mason wrote:
>>
>>> On a tangential subject, as Mans stated, Au1x00 does not support
>>> the scratch register; but Ralink and Tango do. These three
>>> platforms share the weird register layout (requiring the LUTs),
>>> but they differ in scratch support.
>>>
>>> Would it make any sense to differentiate them, to support scratch
>>> where it is implemented? (Although adding offset 7 to au_io_out_map
>>> would then make that table sparse!)
>>
>> A related issue in 8250_early.c
>>
>> probe_baud() and init_port() are using serial8250_early_in() and
>> serial8250_early_out() to read/write the UART registers.
>>
>> unsigned int __weak __init serial8250_early_in(struct uart_port *port, int offset)
>> {
>> switch (port->iotype) {
>> case UPIO_MEM:
>> return readb(port->membase + offset);
>> case UPIO_MEM32:
>> return readl(port->membase + (offset << 2));
>> case UPIO_PORT:
>> return inb(port->iobase + offset);
>> default:
>> return 0;
>> }
>> }
>>
>> These are __weak but I didn't find any overriding implementation.
>> In the UPIO_AU case, I think they are NOPs(?) so how can they work
>> correctly on Ralink/Tango platforms? (Confused)
>
> It doesn't work correctly.
>
>> What is 8250_early.c used for?
>
> As the name implies, it implements an early console that can be used
> before the whole tty/console system has been brought up. Apparently
> nobody bothered adding support for UPIO_AU there.
If there's interest in having earlycon support on this platform,
I can add that pretty easily on top of the same patchset in which
I added Beaglebone Black earlycon.
Regards,
Peter Hurley
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