On 10/21/2015 06:36 AM, Arnd Bergmann wrote: > On Wednesday 21 October 2015 18:30:05 Masahiro Yamada wrote: >>> >>>> I am trying to implement OF_EARLYCON_DECLARE() for that. >>>> >>>> I was just wondering if console_initcall() should work as well. >>>> >>>> >>>> As I said, I noticed the console_initcall() in 8250_core.c >>>> only works on very limited platforms. >>> >>> It works with all those that use of_serial.c, right? >> >> I doubt it. >> >> >> I have a board with a pure 8250-compat device working. >> ( compatible = "ns16550a") >> It uses of_serial.c, of course. >> >> >> As far as I tested, it would never enable the console at console_init(). > > Ok, that sounds like a bug. Peter and others have changed that code > a lot in the last year. I wonder if this has never worked then or > if it has regressed. No, not a bug. console_init() is only for legacy platforms, not for probed drivers. >> The console is enabled when the UART driver is probed. >> (or earlycon if "earlycon" is specified in the kernel-parameter.) > > Got it. Let me know if you think this interpretation is correct: > > * univ8250_console_match() looks for the earlycon argument format like > "console=uart[8250],io|mmio|mmio32,<addr>[,<options>]", and that > would work, but we don't want to have to pass all that data when > the information should already be there. This only works at console_init() time for legacy platforms that have already initialized the 8250 port table. > * univ8250_console_setup() looks for ports that have been added by > one of several other methods (including earlycon) already 8250 earlycon doesn't add ports. > , but we don't do that on ARM without earlycon being enabled. > * arch/powerpc/kernel/legacy_serial.c does everything we need, but > does not live in architecture independent code and does a few > things that we probably don't need or want there. It relies > on scanning the device tree for known UART device nodes before > the platform devices are added. > > * for console_initcall() to do the right thing, we want both the > ttyS devices to get added early for console=ttyS1 to work, as well > as having the preferred console work based on the stdout-property. > > * we parse the /chosen/stdout-path property in drivers/of/base and > store the device node pointer in the global 'of_stdout' variable, > but do not use it until the uart is added by the tty driver > and calls of_console_check() to add the default console device. I'm assuming the issue with trying to get console_init() working is because the dummy color console causes the earlycon to be disabled? I fixed that once before for stdout-path but there were some regressions on PPC platforms; maybe I can revisit that. Regards, Peter Hurley -- 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
