On 03/03/2016 06:35 PM, Peter Hurley wrote: > On 03/03/2016 03:59 AM, Aleksey Makarov wrote: >> >> >> On 03/01/2016 06:31 PM, Peter Hurley wrote: >>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote: >>>> '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. Yes. That's why we have SPCR *and* DBG2. DBG2 specifies where we should run earlycon. >>> How will a user enable an earlycon on the same console as the SPCR >>> console if there is no DBG2 table? In no way. You need DBG2 to run earlycon. (If you don't want to specify it's address etc explicitly) -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
