intel-gtt: maximize ggtt size on platforms that support this

On VT-d supporting platforms the GGTT is allocated in a stolen mem
section separate from graphcis stolen mem. The GMCH register contains
a bitfield specifying the size of that region. Docs suggest that this
region can only be used for GGTT and PPGTT. Hence ensure that the
PPGTT is disabled and use the complete area for the GGTT.

Unfortunately the graphics core on G33/Pineview can't cope with really
large GTTs and the BIOS usually enables the maximum of 512MB. So
don't bother with maximizing the GTT on these platforms.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/char/agp/intel-agp.h

@@ -75,6 +75,8 @@
 #define I810_GMS_DISABLE	0x00000000
 #define I810_PGETBL_CTL		0x2020
 #define I810_PGETBL_ENABLED	0x00000001
+/* Note: PGETBL_CTL2 has a different offset on G33. */
+#define I965_PGETBL_CTL2	0x20c4
 #define I965_PGETBL_SIZE_MASK	0x0000000e
 #define I965_PGETBL_SIZE_512KB	(0 << 1)
 #define I965_PGETBL_SIZE_256KB	(1 << 1)
@@ -82,9 +84,15 @@
 #define I965_PGETBL_SIZE_1MB	(3 << 1)
 #define I965_PGETBL_SIZE_2MB	(4 << 1)
 #define I965_PGETBL_SIZE_1_5MB	(5 << 1)
-#define G33_PGETBL_SIZE_MASK    (3 << 8)
-#define G33_PGETBL_SIZE_1M      (1 << 8)
-#define G33_PGETBL_SIZE_2M      (2 << 8)
+#define G33_GMCH_SIZE_MASK	(3 << 8)
+#define G33_GMCH_SIZE_1M	(1 << 8)
+#define G33_GMCH_SIZE_2M	(2 << 8)
+#define G4x_GMCH_SIZE_MASK	(0xf << 8)
+#define G4x_GMCH_SIZE_1M	(0x1 << 8)
+#define G4x_GMCH_SIZE_2M	(0x3 << 8)
+#define G4x_GMCH_SIZE_VT_1M	(0x9 << 8)
+#define G4x_GMCH_SIZE_VT_1_5M	(0xa << 8)
+#define G4x_GMCH_SIZE_VT_2M	(0xc << 8)
 
 #define I810_DRAM_CTL		0x3000
 #define I810_DRAM_ROW_0		0x00000001

drivers/char/agp/intel-gtt.c

@@ -642,12 +642,47 @@ static unsigned int intel_gtt_stolen_entries(void)
 	return stolen_entries;
 }
 
-static unsigned int intel_gtt_total_entries(void)
+static void i965_adjust_pgetbl_size(unsigned int size_flag)
 {
-	int size;
+	u32 pgetbl_ctl, pgetbl_ctl2;
+
+	/* ensure that ppgtt is disabled */
+	pgetbl_ctl2 = readl(intel_private.registers+I965_PGETBL_CTL2);
+	pgetbl_ctl2 &= ~I810_PGETBL_ENABLED;
+	writel(pgetbl_ctl2, intel_private.registers+I965_PGETBL_CTL2);
+
+	/* write the new ggtt size */
+	pgetbl_ctl = readl(intel_private.registers+I810_PGETBL_CTL);
+	pgetbl_ctl &= ~I965_PGETBL_SIZE_MASK;
+	pgetbl_ctl |= size_flag;
+	writel(pgetbl_ctl, intel_private.registers+I810_PGETBL_CTL);
+}
 
-	if (IS_G33 || INTEL_GTT_GEN == 4 || INTEL_GTT_GEN == 5) {
+static unsigned int i965_gtt_total_entries(void)
+{
+	int size;
 	u32 pgetbl_ctl;
+	u16 gmch_ctl;
+
+	pci_read_config_word(intel_private.bridge_dev,
+			     I830_GMCH_CTRL, &gmch_ctl);
+
+	if (INTEL_GTT_GEN == 5) {
+		switch (gmch_ctl & G4x_GMCH_SIZE_MASK) {
+		case G4x_GMCH_SIZE_1M:
+		case G4x_GMCH_SIZE_VT_1M:
+			i965_adjust_pgetbl_size(I965_PGETBL_SIZE_1MB);
+			break;
+		case G4x_GMCH_SIZE_VT_1_5M:
+			i965_adjust_pgetbl_size(I965_PGETBL_SIZE_1_5MB);
+			break;
+		case G4x_GMCH_SIZE_2M:
+		case G4x_GMCH_SIZE_VT_2M:
+			i965_adjust_pgetbl_size(I965_PGETBL_SIZE_2MB);
+			break;
+		}
+	}
+
 	pgetbl_ctl = readl(intel_private.registers+I810_PGETBL_CTL);
 
 	switch (pgetbl_ctl & I965_PGETBL_SIZE_MASK) {
@@ -660,6 +695,7 @@ static unsigned int intel_gtt_total_entries(void)
 	case I965_PGETBL_SIZE_512KB:
 		size = KB(512);
 		break;
+	/* GTT pagetable sizes bigger than 512KB are not possible on G33! */
 	case I965_PGETBL_SIZE_1MB:
 		size = KB(1024);
 		break;
@@ -676,7 +712,15 @@ static unsigned int intel_gtt_total_entries(void)
 	}
 
 	return size/4;
-	} else if (INTEL_GTT_GEN == 6) {
+}
+
+static unsigned int intel_gtt_total_entries(void)
+{
+	int size;
+
+	if (IS_G33 || INTEL_GTT_GEN == 4 || INTEL_GTT_GEN == 5)
+		return i965_gtt_total_entries();
+	else if (INTEL_GTT_GEN == 6) {
 		u16 snb_gmch_ctl;
 
 		pci_read_config_word(intel_private.pcidev, SNB_GMCH_CTRL, &snb_gmch_ctl);