[XS] Change in coreboot[main]: nb/haswell: Fully disable iGPU when dGPU is used

[Leah Rowe (Code Review)]

Leah Rowe has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/81644?usp=email )

Change subject: nb/haswell: Fully disable iGPU when dGPU is used
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nb/haswell: Fully disable iGPU when dGPU is used

My earlier patch disabled decode *and* disabled the iGPU itself, but
a subsequent revision disabled only VGA decode. Upon revisiting, I
found that, actually, yes, you also need to disable the iGPU entirely.

Tested on Dell 9020 SFF using broadwell MRC, with both iGPU and dGPU.
With this patch, the iGPU is completely disabled when you install a
graphics card, but the iGPU is available to use when no graphics card
is present.

For more context, see:

Author: Leah Rowe 
Date:   Fri Feb 23 13:33:31 2024 +0000

nb/haswell: Disable iGPU when dGPU is used

And now, look at the Gerrit comments for explanation:

https://review.coreboot.org/c/coreboot/+/80717/

So, my original submission on change 80717 was actually correct.
This patch fixes the issue. I tested on iGPU and dGPU, with both
broadwell and haswell mrc.bin.

Change-Id: I944123d41ba0e69d74de424e655de33691089c85
Signed-off-by: Leah Rowe 
---
M src/northbridge/intel/haswell/gma.c
1 file changed, 3 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/44/81644/1

diff --git a/src/northbridge/intel/haswell/gma.c b/src/northbridge/intel/haswell/gma.c
index 48a0ba5..f0b8488 100644
--- a/src/northbridge/intel/haswell/gma.c
+++ b/src/northbridge/intel/haswell/gma.c
@@ -465,6 +465,9 @@
 {
    /* Disable VGA decode */
    pci_or_config16(pcidev_on_root(0, 0), GGC, 1 << 1);
+
+	/* Required or else the graphics card doesn't work */
+	dev->enabled = 0;
 }

static struct device_operations gma_func0_ops = {