1 files changed, 106 insertions, 0 deletions
diff --git a/chip/lm4/peci.c b/chip/lm4/peci.c
new file mode 100644
index 0000000000..fc0d09f71d
--- /dev/null
+++ b/chip/lm4/peci.c
@@ -0,0 +1,106 @@
+/* Copyright (c) 2012 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.
+ */
+
+/* PECI interface for Chrome EC */
+
+#include "board.h"
+#include "console.h"
+#include "gpio.h"
+#include "peci.h"
+#include "registers.h"
+#include "uart.h"
+#include "util.h"
+
+/* Max junction temperature for processor in degrees C */
+/* TODO: read TjMax from processor via PECI */
+#define PECI_TJMAX 105
+
+/* Initial PECI baud rate */
+#define PECI_BAUD_RATE 150000
+
+/* Polling interval for PECI, in ms */
+#define PECI_POLL_INTERVAL_MS 200
+
+/* Internal and external path delays, in ns */
+#define PECI_TD_FET_NS 25  /* Guess; TODO: what is real delay */
+#define PECI_TD_INT_NS 80
+
+
+/* Configures the GPIOs for the PECI module. */
+static void configure_gpios(void)
+{
+	/* PJ6 alternate function 1 = PECI Tx */
+	gpio_set_alternate_function(LM4_GPIO_J, 0x40, 1);
+
+	/* PJ7 analog input = PECI Rx (comparator) */
+	LM4_GPIO_DEN(LM4_GPIO_J) &= ~0x80;
+}
+
+
+int peci_get_cpu_temp(void)
+{
+	int v = LM4_PECI_M0D0 & 0xffff;
+
+	if (v >= 0x8000 && v <= 0x8fff)
+		return -1;
+
+	return v >> 6;
+}
+
+
+int peci_temp_sensor_read(const struct temp_sensor_t* sensor)
+{
+	if (sensor->id != TEMP_SENSOR_CPU_PECI)
+		return EC_ERROR_INVAL;
+
+	return peci_get_cpu_temp();
+}
+
+/*****************************************************************************/
+/* Console commands */
+
+static int command_peci_temp(int argc, char **argv)
+{
+	int t = peci_get_cpu_temp();
+	if (t == -1) {
+		uart_puts("Error reading CPU temperature via PECI\n");
+		uart_printf("Error code = 0x%04x\n", LM4_PECI_M0D0 & 0xffff);
+		return EC_ERROR_UNKNOWN;
+	}
+	uart_printf("Current CPU temperature = %d K = %d C\n", t, t - 273);
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(pecitemp, command_peci_temp);
+
+/*****************************************************************************/
+/* Initialization */
+
+int peci_init(void)
+{
+	volatile uint32_t scratch  __attribute__((unused));
+	int baud;
+
+	/* Enable the PECI module and delay a few clocks */
+	LM4_SYSTEM_RCGCPECI = 1;
+	scratch = LM4_SYSTEM_RCGCPECI;
+
+	/* Configure GPIOs */
+	configure_gpios();
+
+	/* Calculate baud setting from desired rate, compensating for internal
+	 * and external delays. */
+	baud = CPU_CLOCK / (4 * PECI_BAUD_RATE) - 2;
+	baud -= (CPU_CLOCK / 1000000) * (PECI_TD_FET_NS + PECI_TD_INT_NS)
+		/ 1000;
+
+	/* Set baud rate and polling rate */
+	LM4_PECI_DIV = (baud << 16) |
+		(PECI_POLL_INTERVAL_MS * (CPU_CLOCK / 1000 / 4096));
+
+	/* Set up temperature monitoring to report in degrees K */
+	LM4_PECI_CTL = ((PECI_TJMAX + 273) << 22) | 0x2001;
+
+	return EC_SUCCESS;
+}