driver/amd_stt: Add AMD STT driver

Add a driver for writing Skin Temperature Tracking (STT) sensor
readings to the SB-RMI interface. STT readings are used to maximize
the SOc performance while keeping the skin temperature within
specification.

BUG=b:176994331
TEST=Build and run on guybrush
BRANCH=None

Change-Id: If655545158e7dc05946bc67686b1b0b40a40a713
Signed-off-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3078050
Reviewed-by: Bhanu Prakash Maiya <bhanumaiya@google.com>
Reviewed-by: Raul E Rangel <rrangel@chromium.org>
Commit-Queue: Raul E Rangel <rrangel@chromium.org>

6 files changed, 190 insertions, 0 deletions

diff --git a/driver/amd_stt.c b/driver/amd_stt.c
new file mode 100644
index 0000000000..b8ac8dcfba
--- /dev/null
+++ b/driver/amd_stt.c
@@ -0,0 +1,138 @@
+/* Copyright 2021 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "amd_stt.h"
+#include "common.h"
+#include "console.h"
+#include "driver/sb_rmi.h"
+#include "hooks.h"
+#include "math_util.h"
+#include "temp_sensor.h"
+#include "util.h"
+
+/* Debug flag can be toggled with console command: stt debug */
+static bool amd_stt_debug;
+
+/* Console output macros */
+#define CPUTS(outstr) cputs(CC_THERMAL, outstr)
+#define CPRINTS(format, args...) cprints(CC_THERMAL, format, ## args)
+
+static const char * const amd_stt_sensor_name[] = {
+	[AMD_STT_PCB_SENSOR_APU] = "APU",
+	[AMD_STT_PCB_SENSOR_REMOTE] = "Ambient",
+	[AMD_STT_PCB_SENSOR_GPU] = "GPU",
+};
+
+/**
+ * Write temperature sensor value to AP via SB-RMI
+ *
+ * sensor:
+ *	AMD_STT_PCB_SENSOR_APU
+ *	AMD_STT_PCB_SENSOR_REMOTE
+ *	AMD_STT_PCB_SENSOR_GPU
+ *
+ * temp_mk:
+ *	Temperature in degrees milli kelvin
+ */
+static int write_stt_sensor_val(enum amd_stt_pcb_sensor sensor, int temp_mk)
+{
+	uint32_t msgIn = 0;
+	uint32_t msgOut;
+	int temp_mc;
+	int temp_c_fp_msb;
+	int temp_c_fp_lsb;
+
+	temp_mc = MILLI_KELVIN_TO_MILLI_CELSIUS(temp_mk);
+
+	if (amd_stt_debug)
+		CPRINTS("STT: %s = %d.%d °C", amd_stt_sensor_name[sensor],
+			temp_mc / 1000, temp_mc % 1000);
+
+	/* Divide by 1000 to get MSB of fixed point temp */
+	temp_c_fp_msb = temp_mc / 1000;
+	/* Modulus 1000 and multiply by 256/1000 to get LSB of fixed point*/
+	temp_c_fp_lsb = ((temp_mc % 1000) << 8) / 1000;
+
+	/*
+	 * [15:0]: temperature as signed integer with 8 fractional bits.
+	 * [23:16]: sensor index
+	 * [31:24]: unused
+	 */
+	msgIn |= (temp_c_fp_lsb & 0xff);
+	msgIn |= (temp_c_fp_msb & 0xff) << 8;
+	msgIn |= (sensor & 0xff) << 16;
+	return sb_rmi_mailbox_xfer(SB_RMI_WRITE_STT_SENSOR_CMD, msgIn, &msgOut);
+}
+
+static void amd_stt_handler(void)
+{
+	int rv;
+	int soc_temp_mk;
+	int ambient_temp_mk;
+
+	/*
+	 * TODO(b/192391025): Replace with temp_sensor_read_mk(TEMP_SENSOR_SOC)
+	 */
+	rv = board_get_soc_temp_mk(&soc_temp_mk);
+	if (rv) {
+		CPRINTS("STT: Failed to read SOC temp rv:%d", rv);
+		return;
+	}
+
+	rv = write_stt_sensor_val(AMD_STT_PCB_SENSOR_APU, soc_temp_mk);
+	if (rv) {
+		CPRINTS("STT: Failed to write SOC temp rv:%d", rv);
+		return;
+	}
+
+	/*
+	 * TODO(b/192391025): Replace with
+	 *	temp_sensor_read_mk(TEMP_SENSOR_AMBIENT)
+	 */
+	rv = board_get_ambient_temp_mk(&ambient_temp_mk);
+	if (rv) {
+		CPRINTS("STT: Failed to read AMBIENT temp rv:%d", rv);
+		return;
+	}
+
+	rv = write_stt_sensor_val(AMD_STT_PCB_SENSOR_REMOTE, ambient_temp_mk);
+	if (rv) {
+		CPRINTS("STT: Failed to write AMBIENT temp rv:%d", rv);
+		return;
+	}
+}
+DECLARE_HOOK(HOOK_SECOND, amd_stt_handler, HOOK_PRIO_TEMP_SENSOR+1);
+
+static int command_stt(int argc, char **argv)
+{
+	int sensor_id;
+	int temp;
+
+	if (argc < 2)
+		return EC_ERROR_PARAM1;
+	else if (!strcasecmp(argv[1], "debug")) {
+		amd_stt_debug = !amd_stt_debug;
+		return EC_SUCCESS;
+	} else if (argc != 3)
+		return EC_ERROR_PARAM2;
+	else if (!strcasecmp(argv[1],
+			     amd_stt_sensor_name[AMD_STT_PCB_SENSOR_APU]))
+		sensor_id = AMD_STT_PCB_SENSOR_APU;
+	else if (!strcasecmp(argv[1],
+			     amd_stt_sensor_name[AMD_STT_PCB_SENSOR_REMOTE]))
+		sensor_id = AMD_STT_PCB_SENSOR_REMOTE;
+	else if (!strcasecmp(argv[1],
+			     amd_stt_sensor_name[AMD_STT_PCB_SENSOR_GPU]))
+		sensor_id = AMD_STT_PCB_SENSOR_GPU;
+	else
+		return EC_ERROR_PARAM2;
+
+	temp = atoi(argv[2]);
+
+	return write_stt_sensor_val(sensor_id, temp);
+}
+DECLARE_CONSOLE_COMMAND(stt, command_stt,
+			"<apu|ambient|gpu|debug> <temp in mK>",
+			"Write an STT mK temperature to AP");
diff --git a/driver/build.mk b/driver/build.mk
index 0bc42fca47..4ff201c5ce 100644
--- a/driver/build.mk
+++ b/driver/build.mk
@@ -223,3 +223,4 @@ driver-$(CONFIG_MP2964)+=mp2964.o
 
 # SOC Interface
 driver-$(CONFIG_AMD_SB_RMI)+=sb_rmi.o
+driver-$(CONFIG_AMD_STT)+=amd_stt.o
diff --git a/include/config.h b/include/config.h
index a6bd31276d..4e83e96f9c 100644
--- a/include/config.h
+++ b/include/config.h
@@ -3876,6 +3876,9 @@
  */
 #undef CONFIG_TEMP_SENSOR_POWER_GPIO
 
+/* AMD STT (Skin Temperature Tracking) */
+#undef CONFIG_AMD_STT
+
 /* Compile common code for throttling the CPU based on the temp sensors */
 #undef CONFIG_THROTTLE_AP
 
@@ -6434,4 +6437,9 @@
 	 * !CONFIG_ACCELGYRO_BMI_I2C
 	 */
 
+/* AMD STT requires AMD SB-RMI to be enabled */
+#if defined(CONFIG_AMD_STT) && !defined(CONFIG_AMD_SB_RMI)
+#define CONFIG_AMD_SB_RMI
+#endif
+
 #endif  /* __CROS_EC_CONFIG_H */
diff --git a/include/driver/amd_stt.h b/include/driver/amd_stt.h
new file mode 100644
index 0000000000..3d382a6c0a
--- /dev/null
+++ b/include/driver/amd_stt.h
@@ -0,0 +1,27 @@
+/* Copyright 2021 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* AMD STT (Skin Temperature Tracking) Manager */
+
+#ifndef __CROS_EC_AMD_STT_H
+#define __CROS_EC_AMD_STT_H
+
+#define AMD_STT_WRITE_SENSOR_VALUE_CMD 0x3A
+
+enum amd_stt_pcb_sensor {
+	AMD_STT_PCB_SENSOR_APU = 0x0,
+	AMD_STT_PCB_SENSOR_REMOTE = 0x1,
+	AMD_STT_PCB_SENSOR_GPU = 0x2
+};
+
+/**
+ * Boards must implement these callbacks for SOC and Ambient temperature.
+ * Temperature must be returned in Milli Kelvin.
+ * TODO(b/192391025): Replace with direct calls to temp_sensor_read_mk
+ */
+int board_get_soc_temp_mk(int *temp_mk);
+int board_get_ambient_temp_mk(int *temp_mk);
+
+#endif /* __CROS_EC_AMD_STT_H */
diff --git a/zephyr/Kconfig b/zephyr/Kconfig
index b11031b8b4..6253631156 100644
--- a/zephyr/Kconfig
+++ b/zephyr/Kconfig
@@ -802,4 +802,15 @@ config PLATFORM_EC_AMD_SB_RMI
 	  tasks such as managing power consumption and power limits of the CPU
 	  socket.
 
+config PLATFORM_EC_AMD_STT
+	bool "Enable driver for AMD STT interface"
+	depends on PLATFORM_EC_AMD_SB_RMI
+	help
+	  AMD platforms provide the Skin Temperature Tracking (STT) interface.
+	  Skin temperature management can be used to maximize the system
+	  performance while keeping the skin temperature within its
+	  specification. It makes use of the thermal capacitance of the system
+	  to temporarily boost above the sustainable power limit, while the
+	  chassis skin temperatures are below limits.
+
 endif # PLATFORM_EC
diff --git a/zephyr/shim/include/config_chip.h b/zephyr/shim/include/config_chip.h
index d8bb7c27ac..895e19d568 100644
--- a/zephyr/shim/include/config_chip.h
+++ b/zephyr/shim/include/config_chip.h
@@ -1760,4 +1760,9 @@
 #define CONFIG_AMD_SB_RMI
 #endif
 
+#undef CONFIG_AMD_STT
+#ifdef CONFIG_PLATFORM_EC_AMD_STT
+#define CONFIG_AMD_STT
+#endif
+
 #endif  /* __CROS_EC_CONFIG_CHIP_H */