soc/intel/skylake: Use Broadwell as comparision base for Skylake SOC

Use the Broadwell implementation as the comparison base for Skylake.

BRANCH=none
BUG=None
TEST=None

Change-Id: I22eb55ea89eb0d6883f98e4c72a6d243e819e6d8
Signed-off-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-on: http://review.coreboot.org/10340
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/soc/intel/skylake/memmap.c

@@ -0,0 +1,46 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2014 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <arch/io.h>
+#include <cbmem.h>
+#include <device/pci.h>
+#include <soc/pci_devs.h>
+#include <soc/systemagent.h>
+
+static uintptr_t dpr_region_start(void)
+{
+	/*
+	 * Base of DPR is top of usable DRAM below 4GiB. The register has
+	 * 1 MiB alignment and reports the TOP of the range, the base
+	 * must be calculated from the size in MiB in bits 11:4.
+	 */
+	uintptr_t dpr = pci_read_config32(SA_DEV_ROOT, DPR);
+	uintptr_t tom = dpr & ~((1 << 20) - 1);
+
+	/* Subtract DMA Protected Range size if enabled */
+	if (dpr & DPR_EPM)
+		tom -= (dpr & DPR_SIZE_MASK) << 16;
+
+	return tom;
+}
+
+void *cbmem_top(void)
+{
+	return (void *) dpr_region_start();
+}