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

[Alex Villací­s Lasso]

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.

-- 
perl -e '$x=2.4;print sprintf("%.0f + %.0f = %.0f\n",$x,$x,$x+$x);'

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