ec/google/chromeec: add support for retrieving DRAM part number

The DRAM part number can be stored in the CBI data. Therefore, add
support for fetching the DRAM part number from CBI.

BUG=b:112203105
TEST=Fetched data from CBI on phaser during testing.

Change-Id: Ia721c01aab5848ff36e11792adf9c494aa25c01d
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/27945
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/ec/google/chromeec/ec.c

@@ -607,6 +607,31 @@ int google_chromeec_cbi_get_oem_id(uint32_t *id)
 	return cbi_get_uint32(id, CBI_TAG_OEM_ID);
 }
 
+int google_chromeec_cbi_get_dram_part_num(char *buf, size_t bufsize)
+{
+	struct ec_params_get_cbi p = {
+		.tag = CBI_TAG_DRAM_PART_NUM,
+	};
+	struct chromeec_command cmd = {
+		.cmd_code = EC_CMD_GET_CROS_BOARD_INFO,
+		.cmd_version = 0,
+		.cmd_data_in = &p,
+		.cmd_data_out = buf,
+		.cmd_size_in = sizeof(p),
+		.cmd_size_out = bufsize,
+	};
+	int rv;
+
+	rv = google_chromeec_command(&cmd);
+	if (rv < 0)
+		return rv;
+
+	/* Ensure NUL termination. */
+	buf[bufsize - 1] = '\0';
+
+	return 0;
+}
+
 #ifndef __SMM__
 u16 google_chromeec_get_board_version(void)
 {

src/ec/google/chromeec/ec.h

@@ -74,6 +74,7 @@ int google_chromeec_reboot(int dev_idx, enum ec_reboot_cmd type, uint8_t flags);
  */
 int google_chromeec_cbi_get_oem_id(uint32_t *id);
 int google_chromeec_cbi_get_sku_id(uint32_t *id);
+int google_chromeec_cbi_get_dram_part_num(char *buf, size_t bufsize);
 
 /* MEC uses 0x800/0x804 as register/index pair, thus an 8-byte resource. */
 #define MEC_EMI_BASE		0x800

src/ec/google/chromeec/ec_commands.h

@@ -4780,6 +4780,7 @@ enum cbi_data_tag {
 	CBI_TAG_BOARD_VERSION = 0, /* uint16_t or uint8_t[] = {minor,major} */
 	CBI_TAG_OEM_ID = 1,        /* uint8_t */
 	CBI_TAG_SKU_ID = 2,        /* uint8_t */
+	CBI_TAG_DRAM_PART_NUM = 3, /* variable length ascii, nul terminated. */
 	CBI_TAG_COUNT,
 };