161 lines
3.8 KiB
C
161 lines
3.8 KiB
C
/*
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* Intel BayTrail PMIC I2C bus semaphore implementaion
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* Copyright (c) 2014, Intel Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms and conditions of the GNU General Public License,
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* version 2, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*/
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#include <linux/module.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/acpi.h>
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#include <linux/i2c.h>
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#include <linux/interrupt.h>
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#include <asm/iosf_mbi.h>
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#include "i2c-designware-core.h"
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#define SEMAPHORE_TIMEOUT 100
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#define PUNIT_SEMAPHORE 0x7
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static unsigned long acquired;
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static int get_sem(struct device *dev, u32 *sem)
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{
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u32 reg_val;
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int ret;
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ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ, PUNIT_SEMAPHORE,
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®_val);
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if (ret) {
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dev_err(dev, "iosf failed to read punit semaphore\n");
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return ret;
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}
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*sem = reg_val & 0x1;
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return 0;
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}
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static void reset_semaphore(struct device *dev)
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{
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u32 data;
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if (iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
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PUNIT_SEMAPHORE, &data)) {
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dev_err(dev, "iosf failed to reset punit semaphore during read\n");
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return;
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}
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data = data & 0xfffffffe;
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if (iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
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PUNIT_SEMAPHORE, data))
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dev_err(dev, "iosf failed to reset punit semaphore during write\n");
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}
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int baytrail_i2c_acquire(struct dw_i2c_dev *dev)
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{
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u32 sem = 0;
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int ret;
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unsigned long start, end;
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if (!dev || !dev->dev)
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return -ENODEV;
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if (!dev->acquire_lock)
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return 0;
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/* host driver writes 0x2 to side band semaphore register */
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ret = iosf_mbi_write(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_WRITE,
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PUNIT_SEMAPHORE, 0x2);
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if (ret) {
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dev_err(dev->dev, "iosf punit semaphore request failed\n");
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return ret;
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}
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/* host driver waits for bit 0 to be set in semaphore register */
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start = jiffies;
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end = start + msecs_to_jiffies(SEMAPHORE_TIMEOUT);
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while (!time_after(jiffies, end)) {
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ret = get_sem(dev->dev, &sem);
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if (!ret && sem) {
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acquired = jiffies;
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dev_dbg(dev->dev, "punit semaphore acquired after %ums\n",
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jiffies_to_msecs(jiffies - start));
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return 0;
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}
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usleep_range(1000, 2000);
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}
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dev_err(dev->dev, "punit semaphore timed out, resetting\n");
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reset_semaphore(dev->dev);
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ret = iosf_mbi_read(BT_MBI_UNIT_PMC, BT_MBI_BUNIT_READ,
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PUNIT_SEMAPHORE, &sem);
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if (!ret)
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dev_err(dev->dev, "iosf failed to read punit semaphore\n");
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else
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dev_err(dev->dev, "PUNIT SEM: %d\n", sem);
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WARN_ON(1);
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return -ETIMEDOUT;
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}
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EXPORT_SYMBOL(baytrail_i2c_acquire);
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void baytrail_i2c_release(struct dw_i2c_dev *dev)
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{
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if (!dev || !dev->dev)
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return;
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if (!dev->acquire_lock)
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return;
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reset_semaphore(dev->dev);
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dev_dbg(dev->dev, "punit semaphore held for %ums\n",
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jiffies_to_msecs(jiffies - acquired));
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}
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EXPORT_SYMBOL(baytrail_i2c_release);
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int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
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{
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acpi_status status;
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unsigned long long shared_host = 0;
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acpi_handle handle;
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if (!dev || !dev->dev)
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return 0;
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handle = ACPI_HANDLE(dev->dev);
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if (!handle)
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return 0;
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status = acpi_evaluate_integer(handle, "_SEM", NULL, &shared_host);
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if (ACPI_FAILURE(status))
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return 0;
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if (shared_host) {
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dev_info(dev->dev, "I2C bus managed by PUNIT\n");
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dev->acquire_lock = baytrail_i2c_acquire;
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dev->release_lock = baytrail_i2c_release;
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dev->pm_runtime_disabled = true;
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}
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if (!iosf_mbi_available())
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return -EPROBE_DEFER;
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return 0;
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}
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EXPORT_SYMBOL(i2c_dw_eval_lock_support);
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MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
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MODULE_DESCRIPTION("Baytrail I2C Semaphore driver");
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MODULE_LICENSE("GPL v2");
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