Re: [PATCH] ati-vga: Fix framebuffer mapping by using hardware-correct aperture sizes

["Chad Jablonski" <chad@jablonski.xyz>]

>
> For this R100 card APER_SIZE matches MEMSIZE but the BAR length is twice 
> that. Maybe the other card you get will shed some light on what's going on 
> with Radeon. I've looked up what the FCode ROM I've tested was doing. This 
> is from a Card#109-85500-00 Rom#113-85501-226 according to the IDs it sets 
> in the device tree, probably from a PowerMac but I don't have the card 
> just found this ROM. The detokenized part of this Radeon 7000/RV100 ROM 
> that accesses CONFIG_APER_SIZE looks like this:
>
>    7321: const_REG_CONFIG_APER_SIZE
>    7323: ati-reg-l@
>    7325: dup
>    7326: b(to) var_aper_size
>    7329: 2*
>    7330: b(to) var_ram_size
>    7333: const_REG_CONFIG_REG_APER_SIZE
>    7335: ati-reg-l@
>    7337: 2*
>    7338: b(to) var_mmio_size
>
> The variable names were invented by me so it's possible that it actually 
> means vram and mmio BAR size but it does 2* for both the VRAM and REG 
> APERS and this is the size it then uses for map-in and map-out calls so 
> this suggests these registers are half of the BAR size at least for this 
> card.
>

I got the card! It looks like it was exactly as you suspected and I
think this matches with what you're seeing in the FCode. The
CONFIG_APER_SIZE is half of BAR0 for both Rage 128 and R100:

Card                              VRAM    PCI BAR0   CONFIG_MEMSIZE  CONFIG_APER_SIZE  AGP_APER_OFFSET
-----------------------           ----    --------   --------------  ----------------  ---------------
Rage 128 Pro Ultra TF             32MB     64MB       0x02000000      0x02000000        0x02000000
Rage 128 RF/SG AGP                16MB     64MB       0x01000000      0x02000000        0x02000000
Radeon R100 QD [Radeon 7200]      64MB    128MB       0x04000000      0x04000000        N/A
Radeon RV100 QY [Radeon 7000/VE]  32MB    128MB       0x02000000      0x04000000        N/A

>
> I only have a Rage Mobility M6 Design Guide (M6 is another name for RV100) 
> that talks about memory size and it says that it's minimum 8MB maximum 
> 64MB but could be R100 supported more. It's still possible that the BAR 
> size is twice the VRAM size for some reason but we don't have enough 
> evidence for that.
>

Oh! I didn't realize that! That's good to know, I'll dig that up.

I'll include what I learned from the new card and send along a v3 shortly.

- Chad