nb/intel/sandybridge/acpi: Add RMRR entry for iGPU

The iGPU always needs access to its stolen memory. For proper IOMMU
support, we have to make the OS aware of that.

Directly below TOLUD lies the data stolen memory (BDSM) followed by
the GTT stolen memory (BGSM), the iGPU needs access to both.

Change-Id: I391d0a5f1ea14bc90fbacabce41dddfa12b5bb0d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/29668
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

1 files changed, 28 insertions, 1 deletions

diff --git a/src/northbridge/intel/sandybridge/acpi.c b/src/northbridge/intel/sandybridge/acpi.c
index c7914a0a45..48be666367 100644
--- a/src/northbridge/intel/sandybridge/acpi.c
+++ b/src/northbridge/intel/sandybridge/acpi.c
@@ -17,6 +17,7 @@
 
 #include <types.h>
 #include <console/console.h>
+#include <commonlib/helpers.h>
 #include <arch/acpi.h>
 #include <device/device.h>
 #include <device/pci.h>
@@ -66,16 +67,42 @@ unsigned long acpi_fill_mcfg(unsigned long current)
 	return current;
 }
 
+static unsigned long acpi_create_igfx_rmrr(const unsigned long current)
+{
+	const u32 base_mask = ~(u32)(MiB - 1);
+
+	struct device *const host = dev_find_slot(0, PCI_DEVFN(0, 0));
+	if (!host)
+		return 0;
+
+	const u32 bgsm = pci_read_config32(host, BGSM) & base_mask;
+	const u32 tolud = pci_read_config32(host, TOLUD) & base_mask;
+	if (!bgsm || !tolud)
+		return 0;
+
+	return acpi_create_dmar_rmrr(current, 0, bgsm, tolud - 1);
+}
+
 static unsigned long acpi_fill_dmar(unsigned long current)
 {
 	const struct device *const igfx = pcidev_on_root(2, 0);
 
 	if (igfx && igfx->enabled) {
-		const unsigned long tmp = current;
+		unsigned long tmp;
+
+		tmp = current;
 		current += acpi_create_dmar_drhd(current, 0, 0, IOMMU_BASE1);
 		current += acpi_create_dmar_ds_pci(current, 0, 2, 0);
 		current += acpi_create_dmar_ds_pci(current, 0, 2, 1);
 		acpi_dmar_drhd_fixup(tmp, current);
+
+		tmp = current;
+		current += acpi_create_igfx_rmrr(current);
+		if (current != tmp) {
+			current += acpi_create_dmar_ds_pci(current, 0, 2, 0);
+			current += acpi_create_dmar_ds_pci(current, 0, 2, 1);
+			acpi_dmar_rmrr_fixup(tmp, current);
+		}
 	}
 
 	const unsigned long tmp = current;