gfx_uma_size on GM45

[Arthur Heymans]

Hi

On gm45 targets there are some option to set different vram option using
the cmos parameter gfx_uma_size. The northbridge code however allows many
more option, ranging for 1M to 352M. 
So I tried making them an on option by modifying cmos.default and the
northbridge code that uses those cmos bits.
Now the size of this cmos parameter has to be increased for 3 to 4 bits
to be able to hold all those options.

My problem is that only the 3 smallest bits from the cmos parameter are
used.
The problem is truly there because hardcoding the vram size instead
works fine.

these are the changes I tried (at 256M it forgets highest bit and is
read as 0 in cmos and 1M is used):
--- a/src/mainboard/lenovo/x200/cmos.layout
+++ b/src/mainboard/lenovo/x200/cmos.layout
@@ -77,9 +77,9 @@ entries
 940         1       e       1        uwb

# coreboot config options: northbridge
-941         3       e       11       gfx_uma_size
+941         4       e       11       gfx_uma_size

-944         8       h       0        volume
+945         8       h       0        volume

# coreboot config options: check sums
 984          16       h       0        check_sum
@@ -125,12 +125,19 @@ enumerations
 9     1     Primary
 10    0     AHCI
 10    1     Compatible
-11    0     32M
-11    1     48M
-11    2     64M
-11    3     128M
-11    5     96M
-11    6     160M
+11    0     1M
+11    1     4M
+11    2     8M
+11    3     16M
+11    4     32M
+11    5     48M
+11    6     64M
+11    7     128M
+11    8     256M
+11    9     96M
+11    10    160M
+11    11    224M
+11    12    352M

--- a/src/northbridge/intel/gm45/igd.c
+++ b/src/northbridge/intel/gm45/igd.c
@@ -153,10 +153,10 @@ void igd_compute_ggc(sysinfo_t *const sysinfo)
    	/* Graphics Stolen Memory: 2MB GTT (0x0300) when VT-d disabled,
    	   2MB GTT + 2MB shadow GTT (0x0b00) else. */
    	if (get_option(&gfxsize, "gfx_uma_size") != CB_SUCCESS) {
-			/* 0 for 32MB */
-			gfxsize = 0;
+			/* 4 for 32MB, default if not set in cmos */
+			gfxsize = 4;
    	}
-		sysinfo->ggc = 0x0300 | ((gfxsize + 5) << 4);
+		sysinfo->ggc = 0x0300 | ((gfxsize + 1) << 4);
    	if (!(capid & (1 << (48 - 32))))
    		sysinfo->ggc |= 0x0800;
    }

Kind regards

[Peter Stuge]

Hi Arthur,

Arthur Heymans wrote:
> modifying cmos.default and the northbridge code

This is not so easy because it is probably important to ensure
backwards compatibility and there is no infrastructure in place
to do so.

Expect a few man-months of work and another few man-months of
work with upstreaming an actual proper fix of NVRAM in coreboot.

//Peter

[Arthur Heymans]

Peter Stuge  writes:
Hi
> Hi Arthur,
>
> Arthur Heymans wrote:
> > modifying cmos.default and the northbridge code
>
> This is not so easy because it is probably important to ensure
> backwards compatibility and there is no infrastructure in place
> to do so.

I meant cmos.layout...
I don't understand, what you mean by backwards compatibility. The cmos
layout?
get_option(&variable, "cmos parameter") should just get the value in
cmos right?
> Expect a few man-months of work and another few man-months of
> work with upstreaming an actual proper fix of NVRAM in coreboot.

A few man months to correctly read 1 more bit in cmos seems a bit strange.