On 03/03/2016 03:59 AM, Aleksey Makarov wrote:

On 03/01/2016 06:31 PM, Peter Hurley wrote:

quoted

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
Console Redirection Table) [2] as a mandatory ACPI table that
specifies the configuration of serial console.

Introduce a new function acpi_console_check().  At the uart port
registration, this function checks if the ACPI SPCR table specifies
its argument of type struct uart_port to be a console
and if so calls add_preferred_console().

How will a user enable an earlycon on the same console as the SPCR
console if there is no DBG2 table?

...
[    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
[    0.000000] bootconsole [pl11] enabled
...
[    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
...
[    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
[    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
[    0.319502] console [ttyAMA0] enabled
[    0.319502] console [ttyAMA0] enabled
[    0.319933] bootconsole [pl11] disabled
[    0.319933] bootconsole [pl11] disabled
...

Why?

That's pretty disingenuous; via command line?

By that measure, none of your patches are required because a user
can already start both console and earlycon without them.

With the console location specified in the SPCR, earlycon should
be opt-in on the command-line simply with "earlycon" command-line
parameter.