nb/intel/haswell: Handle boards that do not support IGD

Processor graphics is disabled on, for example, the C222 and C224
chipsets.

The change to resource assignment in northbridge.c prevents the following
warning that occurs when the IGD is disabled:

> skipping PCI: 00:00.0@3 fixed resource, size=0!

Tested on a Supermicro X10SLM+-F, which has the IGD disabled by the
chipset. The graphics memory is reclaimed and no issues were observed.

Also tested on an ASRock H81M-HDS. This board has an IGD, but no
regressions were observed.

Change-Id: I86d4aef50b6588f08b86c9758a4b95ccd65e9a96
Signed-off-by: Tristan Corrick <tristan@corrick.kiwi>
Reviewed-on: https://review.coreboot.org/c/30271
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

3 files changed, 41 insertions, 19 deletions

diff --git a/src/northbridge/intel/haswell/early_init.c b/src/northbridge/intel/haswell/early_init.c
index 861873e80d..e31bb0e72c 100644
--- a/src/northbridge/intel/haswell/early_init.c
+++ b/src/northbridge/intel/haswell/early_init.c
@@ -47,28 +47,41 @@ static void haswell_setup_bars(void)
 
 static void haswell_setup_graphics(void)
 {
-	u32 reg32;
-	u16 reg16;
+	bool igd_enabled;
+	u16 ggc;
 	u8 reg8;
 
 	printk(BIOS_DEBUG, "Initializing Graphics...\n");
 
-	/* Setup IGD memory by setting GGC[7:3] = 1 for 32MB */
-	reg16 = pci_read_config16(PCI_DEV(0,0,0), GGC);
-	reg16 &= ~0x00f8;
-	reg16 |= 1 << 3;
-	/* Program GTT memory by setting GGC[9:8] = 2MB */
-	reg16 &= ~0x0300;
-	reg16 |= 2 << 8;
-	/* Enable VGA decode */
-	reg16 &= ~0x0002;
-	pci_write_config16(PCI_DEV(0,0,0), GGC, reg16);
+	igd_enabled = !!(pci_read_config32(PCI_DEV(0, 0, 0), DEVEN)
+			 & DEVEN_D2EN);
+
+	ggc = pci_read_config16(PCI_DEV(0, 0, 0), GGC);
+	ggc &= ~0x3f8;
+	if (igd_enabled) {
+		ggc |= GGC_GTT_2MB | GGC_IGD_MEM_IN_32MB_UNITS(1);
+		ggc &= ~GGC_DISABLE_VGA_IO_DECODE;
+	} else {
+		ggc |= GGC_GTT_0MB | GGC_IGD_MEM_IN_32MB_UNITS(0) |
+		       GGC_DISABLE_VGA_IO_DECODE;
+	}
+	pci_write_config16(PCI_DEV(0, 0, 0), GGC, ggc);
+
+	if (!igd_enabled) {
+		printk(BIOS_DEBUG, "IGD is disabled.\n");
+		return;
+	}
 
 	/* Enable 256MB aperture */
 	reg8 = pci_read_config8(PCI_DEV(0, 2, 0), MSAC);
 	reg8 &= ~0x06;
 	reg8 |= 0x02;
 	pci_write_config8(PCI_DEV(0, 2, 0), MSAC, reg8);
+}
+
+static void haswell_setup_misc(void)
+{
+	u32 reg32;
 
 	/* Erratum workarounds */
 	reg32 = MCHBAR32(0x5f00);
@@ -128,4 +141,6 @@ void haswell_early_initialization(int chipset_type)
 	haswell_setup_iommu();
 
 	haswell_setup_graphics();
+
+	haswell_setup_misc();
 }
diff --git a/src/northbridge/intel/haswell/haswell.h b/src/northbridge/intel/haswell/haswell.h
index 33818ee4aa..bc2fc60e40 100644
--- a/src/northbridge/intel/haswell/haswell.h
+++ b/src/northbridge/intel/haswell/haswell.h
@@ -54,6 +54,11 @@
 #define DMIBAR		0x68
 
 #define GGC		0x50			/* GMCH Graphics Control */
+#define  GGC_DISABLE_VGA_IO_DECODE	(1 << 1)
+#define  GGC_IGD_MEM_IN_32MB_UNITS(x)	(((x) & 0x1f) << 3)
+#define  GGC_GTT_0MB		(0 << 8)
+#define  GGC_GTT_1MB		(1 << 8)
+#define  GGC_GTT_2MB		(2 << 8)
 
 #define DEVEN		0x54			/* Device Enable */
 #define  DEVEN_D7EN	(1 << 14)
diff --git a/src/northbridge/intel/haswell/northbridge.c b/src/northbridge/intel/haswell/northbridge.c
index a803e981e0..fcdb683320 100644
--- a/src/northbridge/intel/haswell/northbridge.c
+++ b/src/northbridge/intel/haswell/northbridge.c
@@ -371,13 +371,15 @@ static void mc_add_dram_resources(struct device *dev, int *resource_cnt)
 			  IORESOURCE_STORED | IORESOURCE_RESERVE |
 			  IORESOURCE_ASSIGNED | IORESOURCE_CACHEABLE;
 
-	/* BGSM -> TOLUD */
-	resource = new_resource(dev, index++);
-	resource->base = mc_values[BGSM_REG];
-	resource->size = mc_values[TOLUD_REG] - resource->base;
-	resource->flags = IORESOURCE_MEM | IORESOURCE_FIXED |
-			  IORESOURCE_STORED | IORESOURCE_RESERVE |
-			  IORESOURCE_ASSIGNED;
+	/* BGSM -> TOLUD. If the IGD is disabled, BGSM can equal TOLUD */
+	if (mc_values[BGSM_REG] != mc_values[TOLUD_REG]) {
+		resource = new_resource(dev, index++);
+		resource->base = mc_values[BGSM_REG];
+		resource->size = mc_values[TOLUD_REG] - resource->base;
+		resource->flags = IORESOURCE_MEM | IORESOURCE_FIXED |
+				  IORESOURCE_STORED | IORESOURCE_RESERVE |
+				  IORESOURCE_ASSIGNED;
+	}
 
 	/* 4GiB -> TOUUD */
 	base_k = 4096 * 1024; /* 4GiB */