radeon_drv and ATI R423

[Mark Maule]

I have an R423 (Fire GL V7100) which I am trying to get running on an IA64
altix platform using the stock radeon driver.  If I run Xorg with
Option "NoAccel" "yes", it appears to come up normally.  If I run with the
default, the card hangs and eventually I get an MCA trying to read RBBM_STATUS.

Using a PCIe analyzer, I've tracked it down to the following code in
RADEONEngineRestore():

...
    RADEONWaitForFifo(pScrn, 7);

    OUTREG(RADEON_DST_LINE_START,    0);
    OUTREG(RADEON_DST_LINE_END,      0);
    OUTREG(RADEON_DP_BRUSH_FRGD_CLR, 0xffffffff);
    OUTREG(RADEON_DP_BRUSH_BKGD_CLR, 0x00000000);
    OUTREG(RADEON_DP_SRC_FRGD_CLR,   0xffffffff);
    OUTREG(RADEON_DP_SRC_BKGD_CLR,   0x00000000);
    OUTREG(RADEON_DP_WRITE_MASK,     0xffffffff);
...

If I remove the store to RADEON_DST_LINE_END, my startup hang goes away.

What I see on an analyzer trace is that after the RADEON_DST_LINE_END store,
the card is generating a 2-byte DMA write to bus address 0, which
never completes and I assume wedges the card.

I'm not using the CP or any DMA, just trying to use basic PIO acceleration.

Is radeon_drv supposed to work with the 423?  I assume it is since I find it
referenced in the code as CHIP_FAMILY_R420.

Any help/advice would be appreciated.

thanks
Mark