nb/intel/sandybridge/mrc: Handle P2P disabling via devicetree

Some Sandy Bridge boards disabled the PCI-to-PCI bridge early to avoid
probing by the MRC. We can do that for all boards instead, based on the
devicetree setting.

Change-Id: Ie64774628fde77db2a379bdba6a921a31e52fa0d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36903
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/northbridge/intel/sandybridge/raminit_mrc.c b/src/northbridge/intel/sandybridge/raminit_mrc.c
index a8acfbf980..29c766a59f 100644
--- a/src/northbridge/intel/sandybridge/raminit_mrc.c
+++ b/src/northbridge/intel/sandybridge/raminit_mrc.c
@@ -18,6 +18,7 @@
 #include <bootmode.h>
 #include <cf9_reset.h>
 #include <string.h>
+#include <device/device.h>
 #include <device/pci_ops.h>
 #include <arch/cpu.h>
 #include <cbmem.h>
@@ -382,6 +383,16 @@ static void devicetree_fill_pei_data(struct pei_data *pei_data)
 	pei_data->usb3.xhci_streams = cfg->usb3.xhci_streams;
 }
 
+static void disable_p2p(void)
+{
+	/* Disable PCI-to-PCI bridge early to prevent probing by MRC. */
+	const struct device *const p2p = pcidev_on_root(0x1e, 0);
+	if (p2p && p2p->enabled)
+		return;
+
+	RCBA32(FD) |= PCH_DISABLE_P2P;
+}
+
 void perform_raminit(int s3resume)
 {
 	int cbmem_was_initted;
@@ -423,6 +434,8 @@ void perform_raminit(int s3resume)
 		}
 	}
 
+	disable_p2p();
+
 	pei_data.boot_mode = s3resume ? 2 : 0;
 	timestamp_add_now(TS_BEFORE_INITRAM);
 	sdram_initialize(&pei_data);