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/* Copyright 2017 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.
*
* Servo state machine.
*/
#include "common.h"
#include "console.h"
#include "gpio.h"
#include "hooks.h"
#include "uart_bitbang.h"
#include "uartn.h"
#include "usb_i2c.h"
#define CPRINTS(format, args...) cprints(CC_SYSTEM, format, ## args)
static enum device_state state = DEVICE_STATE_INIT;
void print_servo_state(void)
{
ccprintf("Servo: %s\n", device_state_name(state));
}
int servo_is_connected(void)
{
/*
* If we're connected, we definitely know we are. If we're debouncing,
* then we were connected and might still be. If we haven't
* initialized yet, we'd bettter assume we're connected until we prove
* otherwise. In any of these cases, it's not safe to allow ports to
* be connected because that would block detecting servo.
*/
return (state == DEVICE_STATE_CONNECTED ||
state == DEVICE_STATE_DEBOUNCING ||
state == DEVICE_STATE_INIT ||
state == DEVICE_STATE_INIT_DEBOUNCING);
}
/**
* Set the servo state.
*
* Done as a function to make it easier to debug state transitions. Note that
* this ONLY sets the state (and possibly prints debug info), and doesn't do
* all the additional transition work that servo_disconnect(), etc. do.
*
* @param new_state State to set.
*/
static void set_state(enum device_state new_state)
{
#ifdef CR50_DEBUG_SERVO_STATE
/* Print all state transitions. May spam the console. */
if (state != new_state)
CPRINTS("Servo %s -> %s",
device_state_name(state), device_state_name(new_state));
#endif
state = new_state;
}
/**
* Check if we can tell servo is connected.
*
* @return 1 if we can tell if servo is connected, 0 if we can't tell.
*/
static int servo_detectable(void)
{
/*
* If we are driving the UART transmit line to the EC, then we can't
* check to see if servo is also doing so.
*
* We also need to check if we're bit-banging the EC UART, because in
* that case, the UART transmit line is directly controlled as a GPIO
* and can be high even if UART TX is disconnected.
*/
return !(uart_tx_is_connected(UART_EC) || uart_bitbang_is_enabled());
}
/**
* Handle servo being disconnected
*/
static void servo_disconnect(void)
{
if (!servo_is_connected())
return;
CPRINTS("Servo disconnect");
set_state(DEVICE_STATE_DISCONNECTED);
ccd_update_state();
}
/**
* Handle servo being connected.
*
* This can be called directly by servo_detect(), or as a deferred function.
* Both are in the HOOK task, so can't preempt each other.
*/
static void servo_connect(void)
{
/*
* If we were debouncing disconnect, go back to connected. We never
* finished disconnecting, so nothing else is necessary.
*/
if (state == DEVICE_STATE_DEBOUNCING)
set_state(DEVICE_STATE_CONNECTED);
/* If we're already connected, nothing else needs to be done */
if (state == DEVICE_STATE_CONNECTED)
return;
/*
* If we're still here, this is a real transition from a disconnected
* state, so we need to configure ports.
*/
CPRINTS("Servo connect");
set_state(DEVICE_STATE_CONNECTED);
ccd_update_state();
}
DECLARE_DEFERRED(servo_connect);
void servo_ignore(int enable)
{
if (enable) {
/*
* Set servo state to IGNORE, so servo presence wont prevent
* cr50 from enabling EC and AP uart.
*/
set_state(DEVICE_STATE_IGNORED);
ccd_update_state();
} else {
/*
* To be on the safe side 'connect' servo when we stop ignoring
* the servo state. If servo is disconnected, then cr50 will
* notice within 1 second and reenable ccd.
*/
servo_connect();
}
}
/**
* Servo state machine
*/
static void servo_detect(void)
{
/* Disable interrupts if we had them on for debouncing */
gpio_disable_interrupt(GPIO_DETECT_SERVO);
if (state == DEVICE_STATE_IGNORED)
return;
/* If we're driving EC UART TX, we can't detect servo */
if (!servo_detectable()) {
/* We're driving one port; might as well drive them all */
servo_disconnect();
set_state(DEVICE_STATE_UNDETECTABLE);
return;
}
/* Handle detecting servo */
if (gpio_get_level(GPIO_DETECT_SERVO)) {
servo_connect();
return;
}
/*
* If servo has become detectable but wasn't detected above, assume
* it's disconnected.
*
* We know we were driving EC UART TX, so we want to give priority to
* our ability to drive it again. If we went to the debouncing state
* here, then we'd need to wait a second before we could drive it.
*
* This is similar to how if servo was driving EC UART TX, we go to the
* debouncing state below, because we want to give priority to servo
* being able to drive it again.
*/
if (state == DEVICE_STATE_UNDETECTABLE) {
set_state(DEVICE_STATE_DISCONNECTED);
return;
}
/*
* Make sure the interrupt is enabled. We will need to detect the on
* transition if we enter the off or debouncing state
*/
gpio_enable_interrupt(GPIO_DETECT_SERVO);
/* Servo wasn't detected. If we're already disconnected, done. */
if (state == DEVICE_STATE_DISCONNECTED)
return;
/* If we were debouncing, we're now sure we're disconnected */
if (state == DEVICE_STATE_DEBOUNCING ||
state == DEVICE_STATE_INIT_DEBOUNCING) {
servo_disconnect();
return;
}
/*
* Otherwise, we were connected or initializing, and we're not sure if
* we're now disconnected or just sending a 0-bit. So start
* debouncing.
*
* During debouncing, servo_is_connected() will still return true, so
* that if both CCD and servo cables are connected, we won't start
* driving EC UART TX and become unable to determine the servo connect
* state.
*/
if (state == DEVICE_STATE_INIT)
set_state(DEVICE_STATE_INIT_DEBOUNCING);
else
set_state(DEVICE_STATE_DEBOUNCING);
}
/*
* Do this at slightly elevated priority so it runs before rdd_check_pin() and
* ec_detect(). This increases the odds that we'll detect servo before
* detecting the EC. If ec_detect() ran first, it could turn on TX to the EC
* UART before we had a chance to detect servo. This is still a little bit of
* a race condition.
*/
DECLARE_HOOK(HOOK_SECOND, servo_detect, HOOK_PRIO_DEFAULT - 1);
/**
* Interrupt handler for servo detect asserted
*/
void servo_detect_asserted(enum gpio_signal signal)
{
gpio_disable_interrupt(GPIO_DETECT_SERVO);
/*
* If this interrupt is because servo is actually detectable (vs. we're
* driving the detect pin now), queue a transition back to connected.
*/
if (servo_detectable())
hook_call_deferred(&servo_connect_data, 0);
}
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