radeonfb.c flakiness

Benjamin Herrenschmidt benh at kernel.crashing.org
Mon Feb 18 08:51:21 EST 2002

>Even with all of my changes, it seems the DFP screen will randomly stay
>blank under PPC Linux.
>Unfortunately, nothing I do can seem to bring it back to life (but all
>of the radeon debug info is absolutely fine).
>So some how we are not properly resetting the 7500 card or not properly
>initializing it.

Try removing the bit of code in my radeonfb.c that blast various
registers like MC_FB_LOCATION within a #ifdef CONFIG_ALL_PPC
in radeon_pci_register().

I suspect the sequence for changing those isn't good, the chip may
need some additional reset or delays.

>I can't understnad why the screen simply goes blank immediately after
>the kernel starts to boot.
>Ben, you mentioned something about playig with the memory mapping of the
>card.  I see code that does something along those lines in the
>radeonfb.c for screens that have dual heads.
>Do you have any ideas I should test to see if they impact the random
>startup blank screen issue (btw the kernel boots fine and I can blindly
>login and shutdown).  Changing VTs from 1 to 2 or 3 has no impact.
>Ideas welcome.

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