nb/intel/i945: Put stage cache in TSEG

TSEG is not accessible in ring 0 after it is locked in ramstage, in
contrast with cbmem which remains accessible. Assuming SMM does not
touch the cache this is a good region to cache stages.

Tested on Intel D945GCLF and Lenovo Thinkpad X60, on cold boot the
external stage cache gets created and the stage cache gets properly
used on S3 resume.

Change-Id: I447815bb0acf5f8e53834b74785d496f9d4df1da
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/25603
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/i945/Kconfig

@@ -31,6 +31,7 @@ config NORTHBRIDGE_SPECIFIC_OPTIONS # dummy
 	select POSTCAR_CONSOLE
 	select SMM_TSEG
 	select PARALLEL_MP
+	select CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM
 
 config NORTHBRIDGE_INTEL_SUBTYPE_I945GC
 	def_bool n
@@ -90,4 +91,8 @@ config CHECK_SLFRCS_ON_RESUME
 	  On other boards the check always creates a false positive,
 	  effectively making it impossible to resume.
 
+config SMM_RESERVED_SIZE
+	hex
+	default 0x100000
+
 endif

src/northbridge/intel/i945/Makefile.inc

@@ -31,4 +31,8 @@ smm-y += udelay.c
 
 postcar-y += ram_calc.c
 
+romstage-$(CONFIG_CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM) += stage_cache.c
+ramstage-$(CONFIG_CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM) += stage_cache.c
+postcar-$(CONFIG_CACHE_RELOCATED_RAMSTAGE_OUTSIDE_CBMEM) += stage_cache.c
+
 endif

src/northbridge/intel/i945/stage_cache.c

@@ -0,0 +1,32 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2015 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.
+ */
+
+#include <arch/io.h>
+#include <cbmem.h>
+#include <device/pci.h>
+#include <stage_cache.h>
+#include <cpu/intel/smm/gen1/smi.h>
+#include "i945.h"
+
+void stage_cache_external_region(void **base, size_t *size)
+{
+	/*
+	 * The ramstage cache lives in the TSEG region at RESERVED_SMM_OFFSET.
+	 * The top of RAM is defined to be the TSEG base address.
+	 */
+	*size = CONFIG_SMM_RESERVED_SIZE;
+	*base = (void *)(northbridge_get_tseg_base()
+			 + CONFIG_SMM_RESERVED_SIZE);
+}