Tracking down bug #12503, looking for comment on my theory

[Alex Deucher]

On Jan 17, 2008 11:38 AM, Alex Villací­s Lasso <a_villacis at palosanto.com> wrote:
> Alex Villací­s Lasso escribió:
> > I post this so that the experts on the mailing list can tell me whether
> > my understanding of the problem is sane (or insane). All comments apply
> > to my home machine, which reserves 16M for video memory reports the
> > following on lspci -v:
> >
> > 01:00.0 VGA compatible controller: S3 Inc. VT8375 [ProSavage8 KM266/KL266]
> > (prog-if 00 [VGA])
> >         Subsystem: S3 Inc. VT8375 [ProSavage8 KM266/KL266]
> >         Flags: bus master, 66MHz, medium devsel, latency 32, IRQ 11
> >         Memory at dfe80000 (32-bit, non-prefetchable) [size=512K]
> >         Memory at d0000000 (32-bit, prefetchable) [size=128M]
> >         Expansion ROM at dfe70000 [disabled] [size=64K]
> >         Capabilities: [dc] Power Management version 2
> >         Capabilities: [80] AGP version 2.0
> >
> >
> >
> >
>
>
> > Looking at the code, there are several things that might be wrong with this:
> > 1) Previously, all the areas got mapped with xf86MapPciMem() and the
> > VIDMEM_MMIO flag, and the function sorted out the write-combining later.
> > The proof is that the message (==) SAVAGE(0): Write-combining range
> > (0xd0000000,0x8000000) eventually appeared. Now, all the areas
> > (including MMIO) are being mapped as VIDMEM_FRAMEBUFFER. This can't be
> > right... or is it?
> >
> > src/savage_driver.c line 3163
> > -------------------
> >     if (psav->MmioRegion.memory == NULL) {
> > #ifdef XSERVER_LIBPCIACCESS
> >         err = pci_device_map_range(psav->PciInfo, psav->MmioRegion.base,
> >                                    psav->MmioRegion.size,
> >                                    (PCI_DEV_MAP_FLAG_WRITABLE),
> >                                    & psav->MmioRegion.memory);
> > #else
> >         psav->MmioRegion.memory =
> >             xf86MapPciMem(pScrn->scrnIndex, VIDMEM_FRAMEBUFFER, /* <---
> > Should this be VIDMEM_MMIO instead? */
> >                           psav->PciTag, psav->MmioRegion.base,
> >                           psav->MmioRegion.size);
> >         err = (psav->MmioRegion.memory == NULL) ? errno : 0;
> > #endif
> > -------------------
> > In my opinion, this is the most likely cause of the hang, since videoram
> > detection, MCLK detection, and colormap all require register (MMIO)
> > access, and all of these are affected prior to the hang.
> >
> As I suspected, changing the highlighted VIDMEM_FRAMEBUFFER to
> VIDMEM_MMIO fixes the lockup and lets the X server start up normally.
> Patch attached, already attached to bug #12503. However, now
> acceleration is broken with the patch applied (but no lockups). If any
> of you have a Savage card, could you please test this patch? I would
> eventually like to have it merged into current git.

Yes this patch is correct.  now what happens with accel?  Can you
explain further?

Alex