+CC linux-serial
On Thursday 14 May 2015 06:34 PM, Vineet Gupta wrote:
> On Thursday 14 May 2015 06:23 PM, Arnd Bergmann wrote:
>
> On Thursday 14 May 2015 15:48:42 Alexey Brodkin wrote:
>
>
>> >
>> > chosen {
>> > - bootargs = "console=tty0 console=ttyS3,115200n8 consoleblank=0";
>> > + bootargs = "earlycon=uart8250,mmio32,0xe0022000,115200n8 console=tty0 console=ttyS3,115200n8 consoleblank=0";
>> > };
>> > };
>> >
>
> When you do earlycon with DT, better use a 'stdout-path' property that points
> to the device, and just put 'earlycon' without arguments on the command line.
>
> Arnd
>
>
> Sure ! I tried that once (3.16) and even the dts patch got merged but had to be reverted out !
>
> 2014-07-27 22524b02b17b Revert "ARC: [arcfpga] stdout-path now suffices for earlycon/console"
>
> Let me see if that works again since serial land has seen some significant churn in recent times
>
> Thx for pointing this out !
so specifying console with stdout-path works for me,
- bootargs = "earlycon=uart8250,mmio32,0xf0000000,115200n8 console=tty0
console=ttyS0,115200n8 consoleblank=0 debug";
+ bootargs = "earlycon=uart8250,mmio32,0xf0000000,115200n8";
+ stdout-path = &uart0;
..
But I don't see earlycon working with paramless earlycon
- bootargs = "earlycon=uart8250,mmio32,0xf0000000,115200n8";
+ bootargs = "earlycon";
stdout-path = &uart0;
And I don't see how it would work for others as of 4.1-rc6
Relevant config items I have are:
CONFIG_SERIAL_EARLYCON=y
CONFIG_SERIAL_8250=y
CONFIG_SERIAL_8250_CONSOLE=y
CONFIG_SERIAL_CORE=y
CONFIG_SERIAL_CORE_CONSOLE=y
CONFIG_SERIAL_OF_PLATFORM=y
...
There are 2 earlyparam handlers for earlcon,
(1) param_setup_earlycon() -> setup_earlycon() -> register_console()
(2) setup_of_earlycon() -> early_init_dt_scan_chosen_serial -> of_setup_earlycon()
#1 only works when arg to earlycon is *not NULL*
#2 only works when arg is *NULL*.
For my case, #2 bails out early as __earlycon_of_table happens to be empty.
8071d8a0 T __earlycon_of_table
8071d8a0 000000c4 t __earlycon_of_table_sentinel
This make sense since I don't see any OF_EARLYCON_DECLARE() in 8250 driver.
As a quick hack I added one in 8250/8250_early.c
@@ -152,3 +154,4 @@ static int __init early_serial8250_setup(struct
earlycon_device *device,
}
EARLYCON_DECLARE(uart8250, early_serial8250_setup);
EARLYCON_DECLARE(uart, early_serial8250_setup);
+OF_EARLYCON_DECLARE(uart8250, "ns8250", early_serial8250_setup);
I needed another fine adjustment as of_setup_earlycon() assumes mmio, while it
needs to be memio32 for my case.
@@ -199,7 +199,7 @@ int __init of_setup_earlycon(unsigned long addr,
int err;
struct uart_port *port = &early_console_dev.port;
- port->iotype = UPIO_MEM;
+ port->iotype = UPIO_MEM32;
With this paramless earlycon works.
Now both the above are hacks, but I want to understand if I'm missing something in
ARC port or does core need some adjustments along the lines of above, since
presumably others have it working !
P.S. with respect to the original patch, I would fold it into for-next with change
to stdout-path and keep earlycon as before - we can fix it up later.
Thx,
-vineet
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