Re: Panic at boot on 4/330 with cgfour and cgsix

On Mon, Jan 27, 2025 at 4:29 AM Julian Coleman <[email protected]> wrote:
>
> Hi,
>
> > So as the subject says I'm having problems with these two
> > framebuffers. It seems to be related to the issue reported a few
> > months ago here.
>
> > Luckily my cgfour is still working and I've attached a dmesg from
> > current below. Any help would be appreciated.
>
> > 1152 x 900cpu0: data fault: pc=0xe80112e4 addr=0xfe02a000
> > ser=0x8002<WRITE,SZERR>
>
> I tried to test 4/300 card, but the power supply has failed in my 4/330.
> I'm still puzzled as to exactly what causes the size error for the P4 bus
> write.  Like last time, we could try by trial and error, but it might be
> an extended process.
>
> David's suggestion is good though - if you can check that it boots with an
> earlier kernel, then we could look at the differences in the P4 bus setup,
> which would give us a good starting point.

I sent a reply to David yesterday but I accidentally sent it just to
him and not the list, here it is below.

So I tried to boot a 4.0 kernel as it was the last one to have cgfour
enabled by default and it had the same panic. I suspect this driver
may not have been working for a very long time. However this
framebuffer works fine on sun3 so I believe it's something specific to
sparc. Using printf() I found the line causing the panic is this.

bt->bt_addr = 0;

I've been scratching my head for a while now trying to figure out how
and why this causes it. My only guess is that it only accepts 8 bit
writes. But that would be rather odd as no other sun framebuffer had
that limitation from what I can tell looking at the drivers. Not
really sure where to go from here.