nb/intel/nehalem: Disable PEG and IGD based on devicetree

Tested on Thinkpad X201: PEG device hidden.

Change-Id: Ib378458a55e18cc02fc49b3e6d6939d31dd4aa65
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35744
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/lenovo/x201/devicetree.cb

@@ -48,6 +48,7 @@ chip northbridge/intel/nehalem
 		device pci 00.0 on # Host bridge
 			subsystemid 0x17aa 0x2193
 		end
+		device pci 01.0 off end # PEG
 		device pci 02.0 on # VGA controller
 			subsystemid 0x17aa 0x215a
 		end

src/mainboard/packardbell/ms2290/devicetree.cb

@@ -48,6 +48,7 @@ chip northbridge/intel/nehalem
 		device pci 00.0 on # Host bridge
 			subsystemid 0x1025 0x0379
 		end
+		device pci 01.0 off end # PEG
 		device pci 02.0 on # VGA controller
 			subsystemid 0x1025 0x0379
 		end

src/northbridge/intel/nehalem/nehalem.h

@@ -67,8 +67,6 @@ typedef struct {
 #define D0F0_MCHBAR_HI 0x4c
 #define D0F0_GGC 0x52
 #define D0F0_DEVEN 0x54
-/* Note: Intel's datasheet is broken. Assume the following values are correct */
-#define  DEVEN_PEG60	(1 << 13)
 #define  DEVEN_IGD	(1 << 3)
 #define  DEVEN_PEG10	(1 << 1)
 #define  DEVEN_HOST	(1 << 0)

src/northbridge/intel/nehalem/northbridge.c

@@ -229,6 +229,28 @@ static void northbridge_init(struct device *dev)
 	northbridge_dmi_init(dev);
 }
 
+/* Disable unused PEG devices based on devicetree before PCI enumeration */
+static void nehalem_init(void *const chip_info)
+{
+	u32 deven_mask = UINT32_MAX;
+	const struct device *dev;
+
+	dev = pcidev_on_root(1, 0);
+	if (!dev || !dev->enabled) {
+		printk(BIOS_DEBUG, "Disabling PEG10.\n");
+		deven_mask &= ~DEVEN_PEG10;
+	}
+	dev = pcidev_on_root(2, 0);
+	if (!dev || !dev->enabled) {
+		printk(BIOS_DEBUG, "Disabling IGD.\n");
+		deven_mask &= ~DEVEN_IGD;
+	}
+	const struct device *const d0f0 = pcidev_on_root(0, 0);
+	if (d0f0)
+		pci_update_config32(d0f0, D0F0_DEVEN, deven_mask, 0);
+
+}
+
 static struct pci_operations intel_pci_ops = {
 	.set_subsystem = pci_dev_set_subsystem,
 };
@@ -269,5 +291,6 @@ static void enable_dev(struct device *dev)
 
 struct chip_operations northbridge_intel_nehalem_ops = {
 	CHIP_NAME("Intel i7 (Nehalem) integrated Northbridge")
-	    .enable_dev = enable_dev,
+	.enable_dev = enable_dev,
+	.init = nehalem_init,
 };