On 21/07/16 11:31, Mark Rutland wrote: [...] >>>> + >>>> +> > > > if (*p == 0) >>>> +> > > > > > return 0; >>>> + >>>> +> > > > errno = 0; >>>> + >>>> +> > > > v = strtoull(p, NULL, 0); >>>> + >>>> +> > > > if (errno) >>>> +> > > > > > return 0; >>>> + >>>> +> > > > return v; >>>> +} >>> >>> It looks like the purgatory code expects angel SWI as the earlycon, >> >> Maybe you saw the debug_brk macro in entry.S? I should remove >> that and just loop. > > Ah, sorry. For some reason I got that confused with the sink code. My > bad. > > Now I see that's assuming an 8-bit MMIO register. > >>> whereas many other earlycons exist (with pl011 being extremely popular). >>> Regardless, if we assume a particular UART type, we should explicitly >>> verify that here. Otherwise the purgatory code will likely bring down >>> the system, and it will be very painful to debug. >>> >>> Please explicitly check for the supported earlycon name. >> >> Purgatory just writes bytes to the address given. Are there >> UARTs that don't have TX as the first port? > > I'm not sure, but it's certainly possible. The generic earlycon binding > doesn't guarantee that the first address is a TX register. Even if they > don't exist today, they could in a month's time, so I don't think we > should assume anything. The Exynos UART (drivers/tty/serial/samsung.c) is one which comes to mind as definitely existing, and on arm64 systems to boot. The TX register is at offset 0x20 there. Robin.
