[J-core] working on SH-2 emulator.

[Rich Felker]

On Tue, Sep 06, 2016 at 02:04:48AM -0500, Rob Landley wrote:
> On 09/06/2016 12:53 AM, D. Jeff Dionne wrote:
> > On Sep 6, 2016, at 2:46 PM, BGB <cr88192 at gmail.com> wrote:
> > 
> > Oh, excellent.  This means you have passed all the CPU tests, and dropped into
> > a GDB stub.  Did you implement and test the J2 CAS instruction, or
> patch it out?
> 
> CAS an the two bit-shifts from sh3. (All mentioned on http://j-core.org
> but I really should have better docs.)
> 
> Alas, our arch/sh/configs/j2_defconfig does not appear to have
> EARLY_PRINTK set, most likely because we haven't got an early printk
> driver for our serial device. So you've got to get pretty far along in
> the kernel boot before it dumps the printk buffer out to the serial device.
> 
> (I remember Rich poking at that area before, but I don't remember how it
> turned out. Possibly it's just not enabled in the config?)

EARLY_PRINTK is deprecated and requires arch-specific hooks. The
modern replacement is EARLYCON, and these Kconfig settings:

CONFIG_CMDLINE="console=ttyUL0 earlycon"
CONFIG_SERIAL_EARLYCON=y
CONFIG_SERIAL_UARTLITE=y
CONFIG_SERIAL_UARTLITE_CONSOLE=y

plus an appropriate node in the device tree, like:

	chosen {
		stdout-path = "serial0";
	};

where "serial0" is an alias assigning a name for the uartlite node,
should make it work.

It looks like I somehow omitted CONFIG_SERIAL_EARLYCON=y from
j2_defconfig; I'll make a note to add it.

Rich