Re: [PATCH v3/resend] ARM: shmobile: Add early debugging support using SCIF(A)

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 06 November 2014 13:33:58 Geert Uytterhoeven wrote:
> 
> On Thu, Nov 6, 2014 at 12:53 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Thursday 06 November 2014 12:38:30 Geert Uytterhoeven wrote:
> >> Add serial port debug macros for the SCIF(A) serial ports.
> >> This includes all shmobile SoCs, except for EMEV2.
> 
> > I don't object to this patch going in, but have you looked at doing
> > just earlycon instead? We are still missing some fixmap changes
> 
> I was thinking about earlycon support...
> 
> > before that works on arm32, but in general, early looks nicer than
> 
> Good to know there are still some parts missing.
> 
> > debug_ll because it doesn't require you to build for a particular
> > machine, with the downside that it's not available as early during
> > boot.
> 
> Hence we're gonna need debug_ll anyway?
> So far I only needed it for real early issues.

It depends on whether you were missing it in the past. shmobile
so far only supports early_platform, which isn't quite as
early as earlycon. If early_platform was good enough then
earlycon will work too.

> >> +     {
> >> +             .virtual        = 0xffe40000,
> >> +             .pfn            = __phys_to_pfn(0xffe40000),
> >> +             .length         = SZ_64K,
> >> +             .type           = MT_DEVICE_NONSHARED
> >> +     },
> >> +#endif /* CONFIG_DEBUG_R8A7779_SCIF2 */
> >>  };
> >
> > This should be done automatically if you call debug_ll_io_init() or
> > have an empty map_io() callback.
> 
> On r8a7779 map_io() is not empty, but it didn't cover the SCIF registers,
> cfr. the commit log:
> 
> > >   4. On SoCs using the legacy machine_desc.map_io(), an identity mapping
> > >      of the SCIF(A) registers must be set up in .map_io(). On all but
> > >      r8a7779 this was already done.

Ok. You can of course just call debug_ll_io_init() manually from the
map_io function, it will create the same mapping.

	Arnd