soc/skylake: Make VT-d controllable from CMOS option

Make VT-d enable or disable based on CMOS value "vtd"
1 = Enable
0 = Disable

Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Change-Id: I1aea14968e08ee6af822bd259ca1d462f8926994
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56252
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/soc/intel/skylake/acpi.c

@@ -245,7 +245,7 @@ unsigned long sa_write_acpi_tables(const struct device *const dev,
 	acpi_dmar_t *const dmar = (acpi_dmar_t *)current;
 
 	/* Create DMAR table only if we have VT-d capability. */
-	if (!soc_is_vtd_capable())
+	if (!soc_vtd_enabled())
 		return current;
 
 	printk(BIOS_DEBUG, "ACPI:    * DMAR\n");

src/soc/intel/skylake/chip.c

@@ -509,7 +509,7 @@ void platform_fsp_silicon_init_params_cb(FSPS_UPD *supd)
 	params->PchIoApicBdfValid = 0;
 
 	/* Enable VT-d and X2APIC */
-	if (soc_is_vtd_capable()) {
+	if (soc_vtd_enabled()) {
 		params->VtdBaseAddress[0] = GFXVT_BASE_ADDRESS;
 		params->VtdBaseAddress[1] = VTVC0_BASE_ADDRESS;
 		params->X2ApicOptOut = 0;

src/soc/intel/skylake/include/soc/systemagent.h

@@ -31,7 +31,7 @@
 #define MCH_DDR_POWER_LIMIT_LO	0x58e0
 #define MCH_DDR_POWER_LIMIT_HI	0x58e4
 
-bool soc_is_vtd_capable(void);
+bool soc_vtd_enabled(void);
 
 static const struct sa_mmio_descriptor soc_gfxvt_mmio_descriptor = {
 	GFXVTBAR,

src/soc/intel/skylake/systemagent.c

@@ -6,15 +6,20 @@
 #include <device/pci_ops.h>
 #include <intelblocks/power_limit.h>
 #include <intelblocks/systemagent.h>
+#include <option.h>
 #include <soc/cpu.h>
 #include <soc/iomap.h>
 #include <soc/msr.h>
 #include <soc/pci_devs.h>
 #include <soc/systemagent.h>
+#include <types.h>
 #include "chip.h"
 
-bool soc_is_vtd_capable(void)
+bool soc_vtd_enabled(void)
 {
+	const unsigned int vtd = get_uint_option("vtd", 1);
+	if (!vtd)
+		return false;
 	struct device *const root_dev = pcidev_path_on_root(SA_DEVFN_ROOT);
 	return root_dev &&
 		!(pci_read_config32(root_dev, CAPID0_A) & VTD_DISABLE);
@@ -41,7 +46,7 @@ void soc_add_fixed_mmio_resources(struct device *dev, int *index)
 	sa_add_fixed_mmio_resources(dev, index, soc_fixed_resources,
 			ARRAY_SIZE(soc_fixed_resources));
 
-	if (soc_is_vtd_capable()) {
+	if (soc_vtd_enabled()) {
 		if (is_devfn_enabled(SA_DEVFN_IGD))
 			sa_add_fixed_mmio_resources(dev, index,
 					&soc_gfxvt_mmio_descriptor, 1);