Re: ast2400 woes

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Sat, 2014-06-07 at 09:20 +1000, Benjamin Herrenschmidt wrote:

> IE. Is there a reason why bASTIsVGAEnabled() and vASTEnableVGAMMIO
> use the IO ports ? The latter reads 0x43 and writes 0x43 and 0x42,
> can it be made to always use MMIO 0x3c3 and write 0x3c3 and 0x3c2 ?
> 
> On my AST2400 at least, even when MMIO is disabled, 0x3c3 still
> responds so it works but is that valid for all chips ? Or do I need
> to favor the PIO path if PIO is available in that case for older
> chipsets ?

Note: I have it working now with a couple of patches that i'll send
when I've cleaned them up, though I still need answers to the earlier
questions so we can make sure we don't break earlier chipset support
on x86.

However, YC, the Endian control bits in extended CRTC register A2 seem
to have no effect at all. With a big endian kernel I get the wrong
endian on graphics regardless of the setting of that register !

Is endian swapping supported on the AST2400 ?

Also what is the exact effect of that register ? Does it affect access
from PCI to the framebuffer or does it affect the way the CRTC consumes
pixels from the framebuffer ? Is is supposed to have an effect on
register accesses ?

Cheers,
Ben.