device/dram: Add LPDDR4 utilities

Add lpddr4.c utility file with lpddr4_speed_mhz_to_reported_mts.
Fill in lpddr4_speeds using JDEC 209-4C table 210.
LPDDR4 SPD decoding utilities are not included since there isn't
a present need.

BUG=b:184124605
TEST=Build and run on guybrush

Change-Id: Id8ddfc98fff4255670c50e1ddd4d0a1326265772
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/52745
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/device/dram/Makefile.inc

@@ -1,3 +1,3 @@
-romstage-y += ddr4.c ddr3.c ddr2.c ddr_common.c
+romstage-y += lpddr4.c ddr4.c ddr3.c ddr2.c ddr_common.c
 
-ramstage-y += ddr4.c ddr3.c ddr2.c ddr_common.c spd.c
+ramstage-y += lpddr4.c ddr4.c ddr3.c ddr2.c ddr_common.c spd.c

src/device/dram/lpddr4.c

@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <console/console.h>
+#include <cbmem.h>
+#include <device/device.h>
+#include <device/dram/lpddr4.h>
+#include <string.h>
+#include <memory_info.h>
+#include <smbios.h>
+#include <types.h>
+
+enum lpddr4_speed_grade {
+	LPDDR4_1600,
+	LPDDR4_2400,
+	LPDDR4_3200,
+	LPDDR4_4266
+};
+
+struct lpddr4_speed_attr {
+	uint32_t min_clock_mhz; // inclusive
+	uint32_t max_clock_mhz; // inclusive
+	uint32_t reported_mts;
+};
+
+/**
+ * LPDDR4 speed attributes derived from JEDEC 209-4C table 210
+ *
+ * min_clock_mhz = Previous max_clock_mhz + 1
+ * max_clock_mhz = 1000/min_tCk_avg(ns)
+ * reported_mts  = Standard reported DDR4 speed in MT/s
+ *                 May be slightly less than the actual max MT/s
+ */
+static const struct lpddr4_speed_attr lpddr4_speeds[] = {
+	[LPDDR4_1600] = {
+		.min_clock_mhz = 10,
+		.max_clock_mhz = 800,
+		.reported_mts = 1600
+	},
+	[LPDDR4_2400] = {
+		.min_clock_mhz = 801,
+		.max_clock_mhz = 1200,
+		.reported_mts = 2400
+	},
+	[LPDDR4_3200] = {
+		.min_clock_mhz = 1201,
+		.max_clock_mhz = 1600,
+		.reported_mts = 3200
+	},
+	[LPDDR4_4266] = {
+		.min_clock_mhz = 1601,
+		.max_clock_mhz = 2137,
+		.reported_mts = 4266
+	},
+};
+
+/**
+ * Converts LPDDR4 clock speed in MHz to the standard reported speed in MT/s
+ */
+uint16_t lpddr4_speed_mhz_to_reported_mts(uint16_t speed_mhz)
+{
+	for (enum lpddr4_speed_grade speed = 0; speed < ARRAY_SIZE(lpddr4_speeds); speed++) {
+		const struct lpddr4_speed_attr *speed_attr = &lpddr4_speeds[speed];
+		if (speed_mhz >= speed_attr->min_clock_mhz &&
+		    speed_mhz <= speed_attr->max_clock_mhz) {
+			return speed_attr->reported_mts;
+		}
+	}
+	printk(BIOS_ERR, "ERROR: LPDDR4 speed of %d MHz is out of range", speed_mhz);
+	return 0;
+}

src/include/device/dram/lpddr4.h

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef DEVICE_DRAM_LPDDR4_H
+#define DEVICE_DRAM_LPDDR4_H
+
+/**
+ * @file lpddr4.h
+ *
+ * \brief Utilities for decoding LPDDR4 info
+ */
+
+#include <device/dram/common.h>
+#include <types.h>
+
+/**
+ * Converts LPDDR4 clock speed in MHz to the standard reported speed in MT/s
+ */
+uint16_t lpddr4_speed_mhz_to_reported_mts(uint16_t speed_mhz);
+
+#endif /* DEVICE_DRAM_LPDDR4_H */