Thanks for answering so quickly! :-) On 07/04/2017 14:18, Robin Murphy wrote: > On 07/04/17 12:53, Mason wrote: > >> Did I implement something wrong? >> Why am I not seeing the output of the panic() call, like I do >> with earlyprintk? >> Since tty0 is enabled, why isn't it picking up where palmchip0 >> left off? > > As far as I'm aware, tty0 is a purely virtual console: look further down > still and you'll probably see a second switch over from tty0 to ttyS0, > which will be when the buffered output *actually* starts coming out > again. That's certainly what happens for me, albeit with > "pl11"->"tty0"->"ttyAMA0", (and complete with not realising ttyAMA0 is > still the same port and reprinting the entire log buffer from the top). Right you are! Also, I had not noticed the "print the entire log buffer from the top" issue you mention. [ 0.000000] Booting Linux on physical CPU 0x0 ... [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') [ 0.000000] bootconsole [palmchip0] enabled ... [ 0.014147] Console: colour dummy device 80x30 [ 0.018616] console [tty0] enabled [ 0.022039] bootconsole [palmchip0] disabled [ 0.000000] Booting Linux on physical CPU 0x0 ... [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') [ 0.000000] bootconsole [palmchip0] enabled [ 0.014147] Console: colour dummy device 80x30 [ 0.018616] console [tty0] enabled [ 0.022039] bootconsole [palmchip0] disabled ... [ 0.460630] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled [ 0.462278] 10700.serial: ttyS0 at MMIO 0x10700 (irq = 20, base_baud = 460800) is a Palmchip BK-3103 [ 1.084227] console [ttyS0] enabled > I believe this is something to do with how the DT stdout-path property > is implemented, because with an explicit "console=ttyAMA0" (or ttyS0 in > your case) on the command line instead of relying on stdout-path, the > boot console does switch directly to the real UART without the > intermediate tty0 blind spot. Indeed, an explicit console=ttyS0,115200 does avoid the "dupe the entire log" issue. There is still some "stuttering" involved: [ 0.000000] earlycon: palmchip0 at MMIO 0x00010700 (options '115200n8') [ 0.000000] bootconsole [palmchip0] enabled ... [ 0.745811] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled [ 0.753681] console [ttyS0] disabled [ 0.757426] 10700.serial: ttyS0 at MMIO 0x10700 (irq = 20, base_baud = 460800) is a Palmchip BK-3103 [ 0.766672] console [ttyS0] enabled [ 0.766672] console [ttyS0] enabled [ 0.773726] bootconsole [palmchip0] disabled [ 0.773726] bootconsole [palmchip0] disabled More importantly, it also solves the "hang before panic message" issue: ... [ 0.575937] io scheduler noop registered [ 0.579888] io scheduler deadline registered [ 0.584245] io scheduler cfq registered (default) [ 0.589650] Kernel panic - not syncing: THIS IS A TEST Hopefully, supporting earlycon on this platform can be included in time for v4.12 :-) Greg, Peter, what do you think? ;-) Regards. -- 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
