Re: [PATCH] ARM64: tegra: Add support for Google Pixel C

[Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 07/01/16 17:20, Rob Herring wrote:
> On Thu, Jan 7, 2016 at 10:53 AM, Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> wrote:
>>
>> On 07/01/16 14:11, Arnd Bergmann wrote:
>>> On Thursday 07 January 2016 13:19:44 Jon Hunter wrote:
> 
> [...]
> 
>> Ok so something like this ...
>>
>> diff --git a/drivers/tty/serial/8250/8250_early.c
>> b/drivers/tty/serial/8250/8250_early.c
>> index af62131af21e..4ce6e2b57534 100644
>> --- a/drivers/tty/serial/8250/8250_early.c
>> +++ b/drivers/tty/serial/8250/8250_early.c
>> @@ -141,7 +141,18 @@ int __init early_serial8250_setup(struct
>> earlycon_device *device,
>>         device->con->write = early_serial8250_write;
>>         return 0;
>>  }
>> +
>> +int __init early_serial8250_mem32_setup(struct earlycon_device *device,
>> +                                       const char *options)
>> +{
>> +       device->port.iotype = UPIO_MEM32;
>> +       device->port.regshift = 2;
>> +
>> +       return early_serial8250_setup(device, options);
>> +}
>>  EARLYCON_DECLARE(uart8250, early_serial8250_setup);
>>  EARLYCON_DECLARE(uart, early_serial8250_setup);
>>  OF_EARLYCON_DECLARE(ns16550, "ns16550", early_serial8250_setup);
>>  OF_EARLYCON_DECLARE(ns16550a, "ns16550a", early_serial8250_setup);
>> +OF_EARLYCON_DECLARE(tegra20_uart, "nvidia,tegra20-uart",
>> +                   early_serial8250_mem32_setup);
>>
>>> Would it be possible to handle the "reg-io-width" parsing in
>>> early_serial8250_setup instead of keying it off the string?
>>
>> Good point. I spent a bit of time looking at this, but I cannot see an
>> easy way to do this unless we check for "reg-io-width" and "reg-shift"
>> in early_init_dt_scan_chosen_serial() and pass to of_setup_earlycon(),
>> however, I am guessing that this would not be ideal as this would happen
>> for non-8250 devices. May be that would be ok, but I am not sure.
> 
> There's been one attempt[1] already. It had a few issues easily
> solved, but I haven't seen a follow-up.

Thanks. Adding Paul.

Paul, are you planning a follow-up to your patch? Otherwise, I am happy
to have crack at it. Don't we also need to read the "reg-shift"?

Cheers
Jon