device/dram: Add method for converting MHz to MT/s
Add method for converting DDR4 speed in MHz to MT/s. Checks that MHz is
within a speed grade range.
BUG=b:167155849
TEST=ddr4-test unit test
BRANCH=Zork
Change-Id: I1433f028afb794fe3e397b03f5bd0565494c8130
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45343
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Fagerburg <pfagerburg@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
diff --git a/src/device/dram/ddr4.c b/src/device/dram/ddr4.c
index 429a9d2..e670b20 100644
--- a/src/device/dram/ddr4.c
+++ b/src/device/dram/ddr4.c
@@ -9,6 +9,69 @@
#include <smbios.h>
#include <types.h>
+enum ddr4_speed_grade {
+ DDR4_1600,
+ DDR4_1866,
+ DDR4_2133,
+ DDR4_2400,
+ DDR4_2666,
+ DDR4_2933,
+ DDR4_3200
+};
+
+struct ddr4_speed_attr {
+ uint32_t min_clock_mhz; // inclusive
+ uint32_t max_clock_mhz; // inclusive
+ uint32_t reported_mts;
+};
+
+/**
+ * DDR4 speed attributes derived from JEDEC 79-4C tables 169 & 170
+ *
+ * min_clock_mhz = 1000/max_tCk_avg(ns) + 1
+ * Adding 1 to make minimum inclusive
+ * max_clock_mhz = 1000/min_tCk_avg(ns)
+ * reported_mts = Standard reported DDR4 speed in MT/s
+ * May be 1 less than the actual max MT/s
+ */
+static const struct ddr4_speed_attr ddr4_speeds[] = {
+ [DDR4_1600] = {
+ .min_clock_mhz = 668,
+ .max_clock_mhz = 800,
+ .reported_mts = 1600
+ },
+ [DDR4_1866] = {
+ .min_clock_mhz = 801,
+ .max_clock_mhz = 934,
+ .reported_mts = 1866
+ },
+ [DDR4_2133] = {
+ .min_clock_mhz = 935,
+ .max_clock_mhz = 1067,
+ .reported_mts = 2133
+ },
+ [DDR4_2400] = {
+ .min_clock_mhz = 1068,
+ .max_clock_mhz = 1200,
+ .reported_mts = 2400
+ },
+ [DDR4_2666] = {
+ .min_clock_mhz = 1201,
+ .max_clock_mhz = 1333,
+ .reported_mts = 2666
+ },
+ [DDR4_2933] = {
+ .min_clock_mhz = 1334,
+ .max_clock_mhz = 1466,
+ .reported_mts = 2933
+ },
+ [DDR4_3200] = {
+ .min_clock_mhz = 1467,
+ .max_clock_mhz = 1600,
+ .reported_mts = 3200
+ }
+};
+
typedef enum {
BLOCK_0, /* Base Configuration and DRAM Parameters */
BLOCK_1,
@@ -68,6 +131,21 @@
}
}
+/**
+ * Converts DDR4 clock speed in MHz to the standard reported speed in MT/s
+ */
+uint16_t ddr4_speed_mhz_to_reported_mts(uint16_t speed_mhz)
+{
+ for (enum ddr4_speed_grade speed = 0; speed < ARRAY_SIZE(ddr4_speeds); speed++) {
+ const struct ddr4_speed_attr *speed_attr = &ddr4_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: DDR4 speed of %d MHz is out of range", speed_mhz);
+ return 0;
+}
/**
* \brief Decode the raw SPD data