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/* Copyright 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 "chipset.h"
#include "clock.h"
#include "common.h"
#include "console.h"
#include "gpio.h"
#include "hooks.h"
#include "peci.h"
#include "registers.h"
#include "temp_sensor.h"
#include "util.h"
/* Initial PECI baud rate */
#define PECI_BAUD_RATE 100000
/* Polling interval for PECI, in ms */
#define PECI_POLL_INTERVAL_MS 250
/*
* Internal and external path delays, in ns. The external delay is a
* best-guess measurement, but we're fairly tolerant of a bad guess because
* PECI_BAUD_RATE is slow compared to PECI's actual maximum baud rate.
*/
#define PECI_TD_FET_NS 60
#define PECI_TD_INT_NS 80
/* Number of controller retries. Should be between 0 and 7. */
#define PECI_RETRY_COUNT 4
/* Timing negotiation error bypass. 1 = on. 0 = off. */
#define PECI_ERROR_BYPASS 1
#define TEMP_AVG_LENGTH 4 /* Should be power of 2 */
static int temp_vals[TEMP_AVG_LENGTH];
static int temp_idx;
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_get_val(int idx, int *temp_ptr)
{
int sum = 0;
int success_cnt = 0;
int i;
if (!chipset_in_state(CHIPSET_STATE_ON))
return EC_ERROR_NOT_POWERED;
for (i = 0; i < TEMP_AVG_LENGTH; ++i) {
if (temp_vals[i] >= 0) {
success_cnt++;
sum += temp_vals[i];
}
}
/*
* Require at least two valid samples. When the AP transitions into S0,
* it is possible, depending on the timing of the PECI sample, to read
* an invalid temperature. This is very rare, but when it does happen
* the temperature returned is CONFIG_PECI_TJMAX. Requiring two valid
* samples here assures us that one bad maximum temperature reading
* when entering S0 won't cause us to trigger an over temperature.
*/
if (success_cnt < 2)
return EC_ERROR_UNKNOWN;
*temp_ptr = sum / success_cnt;
return EC_SUCCESS;
}
static void peci_temp_sensor_poll(void)
{
temp_vals[temp_idx] = peci_get_cpu_temp();
temp_idx = (temp_idx + 1) & (TEMP_AVG_LENGTH - 1);
}
DECLARE_HOOK(HOOK_TICK, peci_temp_sensor_poll, HOOK_PRIO_TEMP_SENSOR);
static void peci_freq_changed(void)
{
int freq = clock_get_freq();
int baud;
/* Disable polling while reconfiguring */
LM4_PECI_CTL = 0;
/*
* Calculate baud setting from desired rate, compensating for internal
* and external delays.
*/
baud = freq / (4 * PECI_BAUD_RATE) - 2;
baud -= (freq / 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 * (freq / 1000 / 4096));
/* Set up temperature monitoring to report in degrees K */
LM4_PECI_CTL = ((CONFIG_PECI_TJMAX + 273) << 22) | 0x0001 |
(PECI_RETRY_COUNT << 12) |
(PECI_ERROR_BYPASS << 11);
}
DECLARE_HOOK(HOOK_FREQ_CHANGE, peci_freq_changed, HOOK_PRIO_DEFAULT);
static void peci_init(void)
{
int i;
/* Enable the PECI module in run and sleep modes. */
clock_enable_peripheral(CGC_OFFSET_PECI, 0x1,
CGC_MODE_RUN | CGC_MODE_SLEEP);
/* Configure GPIOs */
gpio_config_module(MODULE_PECI, 1);
/* Set initial clock frequency */
peci_freq_changed();
/* Initialize temperature reading buffer to a valid value. */
for (i = 0; i < TEMP_AVG_LENGTH; ++i)
temp_vals[i] = 300; /* 27 C */
}
DECLARE_HOOK(HOOK_INIT, peci_init, HOOK_PRIO_DEFAULT);
/*****************************************************************************/
/* Console commands */
static int command_peci_temp(int argc, char **argv)
{
int t = peci_get_cpu_temp();
if (t == -1) {
ccprintf("PECI error 0x%04x\n", LM4_PECI_M0D0 & 0xffff);
return EC_ERROR_UNKNOWN;
}
ccprintf("CPU temp = %d K = %d C\n", t, K_TO_C(t));
return EC_SUCCESS;
}
DECLARE_CONSOLE_COMMAND(pecitemp, command_peci_temp,
NULL,
"Print CPU temperature");
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