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df541c6ffd
Previously, it was really confusing whether I2C_PORT_HOST meant the port where the EC was the master, or the port used to talk to the AP. No functional changes, just a global find/replace and some tidying of unused comments. BUG=chrome-os-partner:18343 BRANCH=none TEST=build all platforms; pass unit tests Change-Id: Ia591ba4577d3399729556e0234ba0db3a0e3c5ea Signed-off-by: Randall Spangler <rspangler@chromium.org> Reviewed-on: https://chromium-review.googlesource.com/174546 Reviewed-by: Alec Berg <alecaberg@chromium.org>
105 lines
2.5 KiB
C
105 lines
2.5 KiB
C
/* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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/* I2C arbitration using a pair of GPIO lines */
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#include "chipset.h"
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#include "common.h"
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#include "gpio.h"
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#include "hooks.h"
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#include "i2c.h"
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#include "timer.h"
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#include "util.h"
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/* Time between requesting bus and deciding that we have it */
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#define BUS_SLEW_DELAY_US 10
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/* Time between retrying to see if the AP has released the bus */
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#define BUS_WAIT_RETRY_US 3000
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/* Time to wait until the bus becomes free */
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#define BUS_WAIT_FREE_US (100 * 1000)
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/*
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* This reflects the desired value of GPIO_EC_CLAIM to ensure that the
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* GPIO is driven correctly when re-enabled before AP power on.
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*/
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static char i2c_claimed_by_ec;
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int i2c_claim(int port)
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{
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timestamp_t start;
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if (port != I2C_PORT_MASTER)
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return EC_SUCCESS;
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/* If AP is off, we have the bus */
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if (chipset_in_state(CHIPSET_STATE_ANY_OFF)) {
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i2c_claimed_by_ec = 1;
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return EC_SUCCESS;
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}
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/* Start a round of trying to claim the bus */
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start = get_time();
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do {
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timestamp_t start_retry;
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int waiting = 0;
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/* Indicate that we want to claim the bus */
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gpio_set_level(GPIO_EC_CLAIM, 0);
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usleep(BUS_SLEW_DELAY_US);
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/* Wait for the AP to release it */
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start_retry = get_time();
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while (time_since32(start_retry) < BUS_WAIT_RETRY_US) {
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if (gpio_get_level(GPIO_AP_CLAIM)) {
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/* We got it, so return */
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i2c_claimed_by_ec = 1;
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return EC_SUCCESS;
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}
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if (!waiting)
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waiting = 1;
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}
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/* It didn't release, so give up, wait, and try again */
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gpio_set_level(GPIO_EC_CLAIM, 1);
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usleep(BUS_WAIT_RETRY_US);
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} while (time_since32(start) < BUS_WAIT_FREE_US);
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gpio_set_level(GPIO_EC_CLAIM, 1);
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usleep(BUS_SLEW_DELAY_US);
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i2c_claimed_by_ec = 0;
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panic_puts("Unable to access I2C bus (arbitration timeout)\n");
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return EC_ERROR_BUSY;
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}
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void i2c_release(int port)
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{
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if (port == I2C_PORT_MASTER) {
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/* Release our claim */
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gpio_set_level(GPIO_EC_CLAIM, 1);
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usleep(BUS_SLEW_DELAY_US);
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i2c_claimed_by_ec = 0;
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}
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}
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static void i2c_pre_init_hook(void)
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{
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gpio_set_flags(GPIO_AP_CLAIM, GPIO_PULL_UP);
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gpio_set_level(GPIO_EC_CLAIM, i2c_claimed_by_ec ? 0 : 1);
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gpio_set_flags(GPIO_EC_CLAIM, GPIO_OUTPUT);
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usleep(BUS_SLEW_DELAY_US);
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}
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DECLARE_HOOK(HOOK_CHIPSET_PRE_INIT, i2c_pre_init_hook, HOOK_PRIO_DEFAULT);
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static void i2c_shutdown_hook(void)
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{
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gpio_set_flags(GPIO_AP_CLAIM, GPIO_INPUT);
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gpio_set_flags(GPIO_EC_CLAIM, GPIO_INPUT);
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}
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DECLARE_HOOK(HOOK_CHIPSET_SHUTDOWN, i2c_shutdown_hook, HOOK_PRIO_DEFAULT);
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