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

On 07/01/16 17:20, Rob Herring wrote:

On Thu, Jan 7, 2016 at 10:53 AM, Jon Hunter [off-list ref] wrote:

quoted

On 07/01/16 14:11, Arnd Bergmann wrote:

quoted

On Thursday 07 January 2016 13:19:44 Jon Hunter wrote:

[...]

quoted

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);

quoted

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