chromeos: Implement locating and decoding wifi sar data from VPD

A VPD entry "wifi_sar" needs to be created which contains a heximal
encoded string in length of 40 bytes. get_wifi_sar_limits() function
retrieves and decodes the data from the VPD entry, which would later
be consumed by platform code.

BUG=chrome-os-partner:60821
TEST=Build and boot lars and reef

Change-Id: I923b58a63dc1f8a7fdd685cf1c618b2fdf4e7061
Signed-off-by: Robbie Zhang <robbie.zhang@intel.com>
Reviewed-on: https://review.coreboot.org/17958
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

3 files changed, 62 insertions, 0 deletions

diff --git a/src/vendorcode/google/chromeos/Makefile.inc b/src/vendorcode/google/chromeos/Makefile.inc
index e84eb3d231..878b0684c0 100644
--- a/src/vendorcode/google/chromeos/Makefile.inc
+++ b/src/vendorcode/google/chromeos/Makefile.inc
@@ -25,6 +25,7 @@ ramstage-$(CONFIG_CHROMEOS_RAMOOPS) += ramoops.c
 romstage-y += vpd_decode.c
 ramstage-y += vpd_decode.c cros_vpd.c vpd_mac.c vpd_serialno.c vpd_calibration.c
 ramstage-$(CONFIG_HAVE_REGULATORY_DOMAIN) += wrdd.c
+ramstage-$(CONFIG_USE_SAR) += sar.c
 ifeq ($(CONFIG_ARCH_MIPS),)
 bootblock-y += watchdog.c
 ramstage-y += watchdog.c
diff --git a/src/vendorcode/google/chromeos/cros_vpd.h b/src/vendorcode/google/chromeos/cros_vpd.h
index 96ca8af329..1fa56a4725 100644
--- a/src/vendorcode/google/chromeos/cros_vpd.h
+++ b/src/vendorcode/google/chromeos/cros_vpd.h
@@ -8,6 +8,7 @@
 #define __CROS_VPD_H__
 
 #define CROS_VPD_REGION_NAME "region"
+#define CROS_VPD_WIFI_SAR_NAME "wifi_sar"
 
 /*
  * Reads VPD string value by key.
diff --git a/src/vendorcode/google/chromeos/sar.c b/src/vendorcode/google/chromeos/sar.c
new file mode 100644
index 0000000000..2b61e223d5
--- /dev/null
+++ b/src/vendorcode/google/chromeos/sar.c
@@ -0,0 +1,60 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2017 Intel Corp.
+ *
+ * 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 <console/console.h>
+#include <types.h>
+#include <string.h>
+#include <sar.h>
+#include "cros_vpd.h"
+
+/* Retrieve the wifi SAR limits data from VPD and decode it */
+int get_wifi_sar_limits(struct wifi_sar_limits *sar_limits)
+{
+	const char *wifi_sar_limit_key = CROS_VPD_WIFI_SAR_NAME;
+	/*
+	 * cros_vpd_gets() reads in one less than size characters from the VPD
+	 * with a terminating null byte ('\0') stored as the last character into
+	 * the buffer, thus the increasing by 1 for buffer_size.
+	 */
+	const size_t buffer_size = (sizeof(struct wifi_sar_limits) /
+				    sizeof(uint8_t)) * 2 + 1;
+	char wifi_sar_limit_str[buffer_size];
+	uint8_t bin_buffer[sizeof(struct wifi_sar_limits)];
+
+	/* Try to read the SAR limit entry from VPD */
+	if (!cros_vpd_gets(wifi_sar_limit_key, wifi_sar_limit_str,
+		ARRAY_SIZE(wifi_sar_limit_str))) {
+		printk(BIOS_ERR,
+			"Error: Could not locate '%s' in VPD\n",
+			wifi_sar_limit_key);
+		return -1;
+	}
+	printk(BIOS_DEBUG, "VPD wifi_sar = %s\n", wifi_sar_limit_str);
+
+	/* Decode the heximal encoded string to binary values */
+	if (hexstrtobin(wifi_sar_limit_str, bin_buffer,
+			sizeof(struct wifi_sar_limits))
+			< sizeof(struct wifi_sar_limits)) {
+		printk(BIOS_ERR,
+			"Error: VPD wifi_sar contains non-heximal value!\n");
+		return -1;
+	}
+
+	/* Fill the sar_limits structure with the decoded data */
+	for (int i = 0; i < NUM_SAR_LIMITS; i++)
+		memcpy(sar_limits->sar_limit[i],
+			&bin_buffer[BYTES_PER_SAR_LIMIT * i],
+			BYTES_PER_SAR_LIMIT);
+	return 0;
+}