Bug#504721: Reason for console detection failure on Sparc Niagara
---------- Forwarded Message ----------
From: David Miller <davem@davemloft.net>
The reason this bug happens is because CONFIG_PROM_CONSOLE is enabled
in the kernel.
It unconditionally gets registered as a real console before the Sun
Hypervisor console driver has a chance to register. The kernel takes
whatever real console registers first, as the highest priority console
(unless specified otherwise on the command line).
This is why the test program that runs to determine the inittab getty
settings doesn't see the console as a "serial" device.
And no, using console=ttyS0 will not fix this problem on Niagara. On
Niagara you would need to use console=ttyHV0.
The only reasonable fix for this bug is to disable CONFIG_PROM_CONSOLE
in the kernel configuration. Nobody should be enabling that kernel
config option on sparc.
It specifically creates this problem because unlike the framebuffer
and serial console drivers, it does not have a way to know whether
it should register or not. The serial and framebuffer drivers check
the PROM indicated device node of the console device, and it only
registers the device as the console if it matches the value of the
'output-device' PROM environment variable setting.
Therefore, having CONFIG_PROM_CONSOLE enabled in the tree is going
to do nothing other than constantly create problems and conflicts
like this. It needs to be turned off, forever.
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