mb/google/ocelot: implement variant_memory_sku()

Ocelot uses the CHROMEOS_DRAM_PART_NUMBER_IN_CBI Kconfig option
because the hardware does not have DRAM ID straps, but this option was
designed for boards that would only ever have a single memory option.

In order to support multiple memory parts, we need to create a table
that maps memory part number to DRAM id so that we can select the
correct SPD for the memory, and then override the variant_memory_sku()
routine so that we can determine and return the correct DRAM id for
the memory part number specified in the CBI.

BUG=b:443646405
TEST=Change DRAM part number in CBI to "H58G66BK7BX067", reboot ocelot
and verify the AP boot logs show that the SPD index = 1.

Change-Id: I18ba6c4891c6053f40e99dcde8a06b9efc1d95f4
Signed-off-by: Nick Vaccaro <nvaccaro@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/89183
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Appukuttan V K <appukuttan.vk@intel.com>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

src/mainboard/google/ocelot/variants/ocelot/Makefile.mk

@@ -4,6 +4,7 @@ bootblock-y += gpio.c
 romstage-y += gpio.c
 romstage-y += memory.c
 romstage-$(CONFIG_FW_CONFIG) += fw_config.c
+romstage-$(CONFIG_CHROMEOS_DRAM_PART_NUMBER_IN_CBI) += part_num_to_dram_id.c
 ramstage-y += gpio.c
 romstage-$(CONFIG_FW_CONFIG) += variant.c
 ramstage-$(CONFIG_FW_CONFIG) += variant.c

src/mainboard/google/ocelot/variants/ocelot/memory.c

@@ -82,7 +82,7 @@ const struct mb_cfg *variant_memory_params(void)
 void variant_get_spd_info(struct mem_spd *spd_info)
 {
 	uint32_t id = board_id() & BOARD_ID_MASK;
-	spd_info->cbfs_index = 0;
+	spd_info->cbfs_index = variant_memory_sku();
 
 	switch (id) {
 	case BOARD_ID_DDR5:

src/mainboard/google/ocelot/variants/ocelot/part_num_to_dram_id.c

@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <baseboard/variants.h>
+
+struct part_num_spd_index {
+	const char part_num[DIMM_INFO_PART_NUMBER_SIZE];
+	int spd_index;
+};
+
+static const struct part_num_spd_index part_number_map[] = {
+	{ "H58G56BK8BX068", 0 },
+	{ "H58G66BK7BX067", 1 },
+	{ "H58G66BK8BX067", 2 },
+	{ "H58GE6AK8BX104", 3 },
+	{ "H58G66CK8BX147", 2 },
+};
+
+int variant_memory_sku(void)
+{
+	int index;
+	size_t num_elements = ARRAY_SIZE(part_number_map);
+	const char *part_num = mainboard_get_dram_part_num();
+
+	if (part_num == NULL)
+		die("No part number in CBI, halting boot.\n");
+
+	for (index = 0; index < num_elements; index++) {
+		if (!strcmp(part_num, part_number_map[index].part_num))
+			/* exact match found */
+			return part_number_map[index].spd_index;
+	}
+
+	/* We didn't find a match for part_num, halt boot */
+	die("No part number found looking for %s, halting boot.\n", part_num);
+}