ec/google/chromeec: Introduce SKU_ID helpers

The following introduces helpers that, by default,
accommodate a larger SKU id space. The following
is the rational for that:

 Allow INT32_MAX SKU id encodings beyond UINT8_MAX.
 This allows for the SKU id to accommodate up to 4 bytes
 however we reserve the highest bit for SKU_UNKNOWN to be encoded.

However, the legacy UINT8_MAX encoding is supported by leveraging
the Kconfig by overriding it with the legacy max of 0xff.

Follow ups migrate boards to this common framework.

V.2: Fixup array size && drop sku_id SKU_UNKNOWN check and pass
     whatever is set to userspace as firmware doesn't care about
     the value.
V.3: Use SPDX-License header.

BUG=b:149348474
BRANCH=none
TEST=tested on hatch.

Change-Id: I805b25465a3b4ee3dc0cbda5feb9e9ea2493ff9e
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39018
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/ec/google/chromeec/Kconfig

@@ -100,6 +100,11 @@ config EC_GOOGLE_CHROMEEC_SPI_CHIP
 	hex
 	default 0x0
 
+config EC_GOOGLE_CHROMEEC_SKUID
+	def_bool n
+	help
+	  Provides common routine for reporting the skuid to ChromeOS.
+
 config EC_GOOGLE_CHROMEEC_BOARDNAME
 	depends on EC_GOOGLE_CHROMEEC
 	string "Chrome EC board name for EC"

src/ec/google/chromeec/Makefile.inc

@@ -6,6 +6,9 @@ romstage-$(CONFIG_EC_GOOGLE_CHROMEEC_BOARDID) += ec_boardid.c
 ramstage-$(CONFIG_EC_GOOGLE_CHROMEEC_BOARDID) += ec_boardid.c
 smm-$(CONFIG_EC_GOOGLE_CHROMEEC_BOARDID) += ec_boardid.c
 
+romstage-$(CONFIG_EC_GOOGLE_CHROMEEC_SKUID) += ec_skuid.c
+ramstage-$(CONFIG_EC_GOOGLE_CHROMEEC_SKUID) += ec_skuid.c
+
 bootblock-y += ec.c
 bootblock-$(CONFIG_EC_GOOGLE_CHROMEEC_LPC) += ec_lpc.c
 ramstage-y += ec.c crosec_proto.c vstore.c

src/ec/google/chromeec/ec.h

@@ -89,6 +89,9 @@ int google_chromeec_cbi_get_fw_config(uint32_t *fw_config);
 int google_chromeec_cbi_get_dram_part_num(char *buf, size_t bufsize);
 int google_chromeec_cbi_get_oem_name(char *buf, size_t bufsize);
 
+uint32_t google_chromeec_get_board_sku(void);
+const char *google_chromeec_smbios_system_sku(void);
+
 /* MEC uses 0x800/0x804 as register/index pair, thus an 8-byte resource. */
 #define MEC_EMI_BASE		0x800
 #define MEC_EMI_SIZE		8

src/ec/google/chromeec/ec_skuid.c

@@ -0,0 +1,36 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2020 The coreboot project Authors.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include <stddef.h>
+#include <boardid.h>
+#include <ec/google/chromeec/ec.h>
+#include <console/console.h>
+#include <string.h>
+
+#define SKU_UNKNOWN		0xFFFFFFFF
+
+uint32_t google_chromeec_get_board_sku(void)
+{
+	MAYBE_STATIC_NONZERO uint32_t sku_id = SKU_UNKNOWN;
+
+	if (sku_id != SKU_UNKNOWN)
+		return sku_id;
+
+	if (google_chromeec_cbi_get_sku_id(&sku_id))
+		sku_id = SKU_UNKNOWN;
+
+	return sku_id;
+}
+
+const char *google_chromeec_smbios_system_sku(void)
+{
+	static char sku_str[14]; /* sku{0..2147483647} */
+	uint32_t sku_id = google_chromeec_get_board_sku();
+	snprintf(sku_str, sizeof(sku_str), "sku%u", sku_id);
+	return sku_str;
+}