Merge tag 'gpio-v3.13-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[linux-2.6.git] / drivers / staging / nvec / nvec.c

/*
 * NVEC: NVIDIA compliant embedded controller interface
 *
 * Copyright (C) 2011 The AC100 Kernel Team <ac100@lists.lauchpad.net>
 *
 * Authors:  Pierre-Hugues Husson <phhusson@free.fr>
 *           Ilya Petrov <ilya.muromec@gmail.com>
 *           Marc Dietrich <marvin24@gmx.de>
 *           Julian Andres Klode <jak@jak-linux.org>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 */

/* #define DEBUG */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/atomic.h>
#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/gpio.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/list.h>
#include <linux/mfd/core.h>
#include <linux/mutex.h>
#include <linux/notifier.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <linux/clk/tegra.h>

#include "nvec.h"

#define I2C_CNFG                        0x00
#define I2C_CNFG_PACKET_MODE_EN         (1<<10)
#define I2C_CNFG_NEW_MASTER_SFM         (1<<11)
#define I2C_CNFG_DEBOUNCE_CNT_SHIFT     12

#define I2C_SL_CNFG             0x20
#define I2C_SL_NEWSL            (1<<2)
#define I2C_SL_NACK             (1<<1)
#define I2C_SL_RESP             (1<<0)
#define I2C_SL_IRQ              (1<<3)
#define END_TRANS               (1<<4)
#define RCVD                    (1<<2)
#define RNW                     (1<<1)

#define I2C_SL_RCVD             0x24
#define I2C_SL_STATUS           0x28
#define I2C_SL_ADDR1            0x2c
#define I2C_SL_ADDR2            0x30
#define I2C_SL_DELAY_COUNT      0x3c

/**
 * enum nvec_msg_category - Message categories for nvec_msg_alloc()
 * @NVEC_MSG_RX: The message is an incoming message (from EC)
 * @NVEC_MSG_TX: The message is an outgoing message (to EC)
 */
enum nvec_msg_category  {
        NVEC_MSG_RX,
        NVEC_MSG_TX,
};

enum nvec_sleep_subcmds {
        GLOBAL_EVENTS,
        AP_PWR_DOWN,
        AP_SUSPEND,
};

#define CNF_EVENT_REPORTING 0x01
#define GET_FIRMWARE_VERSION 0x15
#define LID_SWITCH BIT(1)
#define PWR_BUTTON BIT(15)

static struct nvec_chip *nvec_power_handle;

static struct mfd_cell nvec_devices[] = {
        {
                .name = "nvec-kbd",
                .id = 1,
        },
        {
                .name = "nvec-mouse",
                .id = 1,
        },
        {
                .name = "nvec-power",
                .id = 1,
        },
        {
                .name = "nvec-power",
                .id = 2,
        },
        {
                .name = "nvec-paz00",
                .id = 1,
        },
};

/**
 * nvec_register_notifier - Register a notifier with nvec
 * @nvec: A &struct nvec_chip
 * @nb: The notifier block to register
 *
 * Registers a notifier with @nvec. The notifier will be added to an atomic
 * notifier chain that is called for all received messages except those that
 * correspond to a request initiated by nvec_write_sync().
 */
int nvec_register_notifier(struct nvec_chip *nvec, struct notifier_block *nb,
                           unsigned int events)
{
        return atomic_notifier_chain_register(&nvec->notifier_list, nb);
}
EXPORT_SYMBOL_GPL(nvec_register_notifier);

/**
 * nvec_unregister_notifier - Unregister a notifier with nvec
 * @nvec: A &struct nvec_chip
 * @nb: The notifier block to unregister
 *
 * Unregisters a notifier with @nvec. The notifier will be removed from the
 * atomic notifier chain.
 */
int nvec_unregister_notifier(struct nvec_chip *nvec, struct notifier_block *nb)
{
        return atomic_notifier_chain_unregister(&nvec->notifier_list, nb);
}
EXPORT_SYMBOL_GPL(nvec_unregister_notifier);

/**
 * nvec_status_notifier - The final notifier
 *
 * Prints a message about control events not handled in the notifier
 * chain.
 */
static int nvec_status_notifier(struct notifier_block *nb,
                                unsigned long event_type, void *data)
{
        struct nvec_chip *nvec = container_of(nb, struct nvec_chip,
                                                nvec_status_notifier);
        unsigned char *msg = (unsigned char *)data;

        if (event_type != NVEC_CNTL)
                return NOTIFY_DONE;

        dev_warn(nvec->dev, "unhandled msg type %ld\n", event_type);
        print_hex_dump(KERN_WARNING, "payload: ", DUMP_PREFIX_NONE, 16, 1,
                msg, msg[1] + 2, true);

        return NOTIFY_OK;
}

/**
 * nvec_msg_alloc:
 * @nvec: A &struct nvec_chip
 * @category: Pool category, see &enum nvec_msg_category
 *
 * Allocate a single &struct nvec_msg object from the message pool of
 * @nvec. The result shall be passed to nvec_msg_free() if no longer
 * used.
 *
 * Outgoing messages are placed in the upper 75% of the pool, keeping the
 * lower 25% available for RX buffers only. The reason is to prevent a
 * situation where all buffers are full and a message is thus endlessly
 * retried because the response could never be processed.
 */
static struct nvec_msg *nvec_msg_alloc(struct nvec_chip *nvec,
                                       enum nvec_msg_category category)
{
        int i = (category == NVEC_MSG_TX) ? (NVEC_POOL_SIZE / 4) : 0;

        for (; i < NVEC_POOL_SIZE; i++) {
                if (atomic_xchg(&nvec->msg_pool[i].used, 1) == 0) {
                        dev_vdbg(nvec->dev, "INFO: Allocate %i\n", i);
                        return &nvec->msg_pool[i];
                }
        }

        dev_err(nvec->dev, "could not allocate %s buffer\n",
                (category == NVEC_MSG_TX) ? "TX" : "RX");

        return NULL;
}

/**
 * nvec_msg_free:
 * @nvec: A &struct nvec_chip
 * @msg:  A message (must be allocated by nvec_msg_alloc() and belong to @nvec)
 *
 * Free the given message
 */
void nvec_msg_free(struct nvec_chip *nvec, struct nvec_msg *msg)
{
        if (msg != &nvec->tx_scratch)
                dev_vdbg(nvec->dev, "INFO: Free %ti\n", msg - nvec->msg_pool);
        atomic_set(&msg->used, 0);
}
EXPORT_SYMBOL_GPL(nvec_msg_free);

/**
 * nvec_msg_is_event - Return %true if @msg is an event
 * @msg: A message
 */
static bool nvec_msg_is_event(struct nvec_msg *msg)
{
        return msg->data[0] >> 7;
}

/**
 * nvec_msg_size - Get the size of a message
 * @msg: The message to get the size for
 *
 * This only works for received messages, not for outgoing messages.
 */
static size_t nvec_msg_size(struct nvec_msg *msg)
{
        bool is_event = nvec_msg_is_event(msg);
        int event_length = (msg->data[0] & 0x60) >> 5;

        /* for variable size, payload size in byte 1 + count (1) + cmd (1) */
        if (!is_event || event_length == NVEC_VAR_SIZE)
                return (msg->pos || msg->size) ? (msg->data[1] + 2) : 0;
        else if (event_length == NVEC_2BYTES)
                return 2;
        else if (event_length == NVEC_3BYTES)
                return 3;
        else
                return 0;
}

/**
 * nvec_gpio_set_value - Set the GPIO value
 * @nvec: A &struct nvec_chip
 * @value: The value to write (0 or 1)
 *
 * Like gpio_set_value(), but generating debugging information
 */
static void nvec_gpio_set_value(struct nvec_chip *nvec, int value)
{
        dev_dbg(nvec->dev, "GPIO changed from %u to %u\n",
                gpio_get_value(nvec->gpio), value);
        gpio_set_value(nvec->gpio, value);
}

/**
 * nvec_write_async - Asynchronously write a message to NVEC
 * @nvec: An nvec_chip instance
 * @data: The message data, starting with the request type
 * @size: The size of @data
 *
 * Queue a single message to be transferred to the embedded controller
 * and return immediately.
 *
 * Returns: 0 on success, a negative error code on failure. If a failure
 * occured, the nvec driver may print an error.
 */
int nvec_write_async(struct nvec_chip *nvec, const unsigned char *data,
                        short size)
{
        struct nvec_msg *msg;
        unsigned long flags;

        msg = nvec_msg_alloc(nvec, NVEC_MSG_TX);

        if (msg == NULL)
                return -ENOMEM;

        msg->data[0] = size;
        memcpy(msg->data + 1, data, size);
        msg->size = size + 1;

        spin_lock_irqsave(&nvec->tx_lock, flags);
        list_add_tail(&msg->node, &nvec->tx_data);
        spin_unlock_irqrestore(&nvec->tx_lock, flags);

        schedule_work(&nvec->tx_work);

        return 0;
}
EXPORT_SYMBOL(nvec_write_async);

/**
 * nvec_write_sync - Write a message to nvec and read the response
 * @nvec: An &struct nvec_chip
 * @data: The data to write
 * @size: The size of @data
 *
 * This is similar to nvec_write_async(), but waits for the
 * request to be answered before returning. This function
 * uses a mutex and can thus not be called from e.g.
 * interrupt handlers.
 *
 * Returns: A pointer to the response message on success,
 * %NULL on failure. Free with nvec_msg_free() once no longer
 * used.
 */
struct nvec_msg *nvec_write_sync(struct nvec_chip *nvec,
                const unsigned char *data, short size)
{
        struct nvec_msg *msg;

        mutex_lock(&nvec->sync_write_mutex);

        nvec->sync_write_pending = (data[1] << 8) + data[0];

        if (nvec_write_async(nvec, data, size) < 0) {
                mutex_unlock(&nvec->sync_write_mutex);
                return NULL;
        }

        dev_dbg(nvec->dev, "nvec_sync_write: 0x%04x\n",
                                        nvec->sync_write_pending);
        if (!(wait_for_completion_timeout(&nvec->sync_write,
                                msecs_to_jiffies(2000)))) {
                dev_warn(nvec->dev, "timeout waiting for sync write to complete\n");
                mutex_unlock(&nvec->sync_write_mutex);
                return NULL;
        }

        dev_dbg(nvec->dev, "nvec_sync_write: pong!\n");

        msg = nvec->last_sync_msg;

        mutex_unlock(&nvec->sync_write_mutex);

        return msg;
}
EXPORT_SYMBOL(nvec_write_sync);

/**
 * nvec_toggle_global_events - enables or disables global event reporting
 * @nvec: nvec handle
 * @state: true for enable, false for disable
 *
 * This switches on/off global event reports by the embedded controller.
 */
static void nvec_toggle_global_events(struct nvec_chip *nvec, bool state)
{
        unsigned char global_events[] = { NVEC_SLEEP, GLOBAL_EVENTS, state };

        nvec_write_async(nvec, global_events, 3);
}

/**
 * nvec_event_mask - fill the command string with event bitfield
 * ev: points to event command string
 * mask: bit to insert into the event mask
 *
 * Configure event command expects a 32 bit bitfield which describes
 * which events to enable. The bitfield has the following structure
 * (from highest byte to lowest):
 *      system state bits 7-0
 *      system state bits 15-8
 *      oem system state bits 7-0
 *      oem system state bits 15-8
 */
static void nvec_event_mask(char *ev, u32 mask)
{
        ev[3] = mask >> 16 & 0xff;
        ev[4] = mask >> 24 & 0xff;
        ev[5] = mask >> 0  & 0xff;
        ev[6] = mask >> 8  & 0xff;
}

/**
 * nvec_request_master - Process outgoing messages
 * @work: A &struct work_struct (the tx_worker member of &struct nvec_chip)
 *
 * Processes all outgoing requests by sending the request and awaiting the
 * response, then continuing with the next request. Once a request has a
 * matching response, it will be freed and removed from the list.
 */
static void nvec_request_master(struct work_struct *work)
{
        struct nvec_chip *nvec = container_of(work, struct nvec_chip, tx_work);
        unsigned long flags;
        long err;
        struct nvec_msg *msg;

        spin_lock_irqsave(&nvec->tx_lock, flags);
        while (!list_empty(&nvec->tx_data)) {
                msg = list_first_entry(&nvec->tx_data, struct nvec_msg, node);
                spin_unlock_irqrestore(&nvec->tx_lock, flags);
                nvec_gpio_set_value(nvec, 0);
                err = wait_for_completion_interruptible_timeout(
                                &nvec->ec_transfer, msecs_to_jiffies(5000));

                if (err == 0) {
                        dev_warn(nvec->dev, "timeout waiting for ec transfer\n");
                        nvec_gpio_set_value(nvec, 1);
                        msg->pos = 0;
                }

                spin_lock_irqsave(&nvec->tx_lock, flags);

                if (err > 0) {
                        list_del_init(&msg->node);
                        nvec_msg_free(nvec, msg);
                }
        }
        spin_unlock_irqrestore(&nvec->tx_lock, flags);
}

/**
 * parse_msg - Print some information and call the notifiers on an RX message
 * @nvec: A &struct nvec_chip
 * @msg: A message received by @nvec
 *
 * Paarse some pieces of the message and then call the chain of notifiers
 * registered via nvec_register_notifier.
 */
static int parse_msg(struct nvec_chip *nvec, struct nvec_msg *msg)
{
        if ((msg->data[0] & 1 << 7) == 0 && msg->data[3]) {
                dev_err(nvec->dev, "ec responded %*ph\n", 4, msg->data);
                return -EINVAL;
        }

        if ((msg->data[0] >> 7) == 1 && (msg->data[0] & 0x0f) == 5)
                print_hex_dump(KERN_WARNING, "ec system event ",
                                DUMP_PREFIX_NONE, 16, 1, msg->data,
                                msg->data[1] + 2, true);

        atomic_notifier_call_chain(&nvec->notifier_list, msg->data[0] & 0x8f,
                                   msg->data);

        return 0;
}

/**
 * nvec_dispatch - Process messages received from the EC
 * @work: A &struct work_struct (the tx_worker member of &struct nvec_chip)
 *
 * Process messages previously received from the EC and put into the RX
 * queue of the &struct nvec_chip instance associated with @work.
 */
static void nvec_dispatch(struct work_struct *work)
{
        struct nvec_chip *nvec = container_of(work, struct nvec_chip, rx_work);
        unsigned long flags;
        struct nvec_msg *msg;

        spin_lock_irqsave(&nvec->rx_lock, flags);
        while (!list_empty(&nvec->rx_data)) {
                msg = list_first_entry(&nvec->rx_data, struct nvec_msg, node);
                list_del_init(&msg->node);
                spin_unlock_irqrestore(&nvec->rx_lock, flags);

                if (nvec->sync_write_pending ==
                      (msg->data[2] << 8) + msg->data[0]) {
                        dev_dbg(nvec->dev, "sync write completed!\n");
                        nvec->sync_write_pending = 0;
                        nvec->last_sync_msg = msg;
                        complete(&nvec->sync_write);
                } else {
                        parse_msg(nvec, msg);
                        nvec_msg_free(nvec, msg);
                }
                spin_lock_irqsave(&nvec->rx_lock, flags);
        }
        spin_unlock_irqrestore(&nvec->rx_lock, flags);
}

/**
 * nvec_tx_completed - Complete the current transfer
 * @nvec: A &struct nvec_chip
 *
 * This is called when we have received an END_TRANS on a TX transfer.
 */
static void nvec_tx_completed(struct nvec_chip *nvec)
{
        /* We got an END_TRANS, let's skip this, maybe there's an event */
        if (nvec->tx->pos != nvec->tx->size) {
                dev_err(nvec->dev, "premature END_TRANS, resending\n");
                nvec->tx->pos = 0;
                nvec_gpio_set_value(nvec, 0);
        } else {
                nvec->state = 0;
        }
}

/**
 * nvec_rx_completed - Complete the current transfer
 * @nvec: A &struct nvec_chip
 *
 * This is called when we have received an END_TRANS on a RX transfer.
 */
static void nvec_rx_completed(struct nvec_chip *nvec)
{
        if (nvec->rx->pos != nvec_msg_size(nvec->rx)) {
                dev_err(nvec->dev, "RX incomplete: Expected %u bytes, got %u\n",
                           (uint) nvec_msg_size(nvec->rx),
                           (uint) nvec->rx->pos);

                nvec_msg_free(nvec, nvec->rx);
                nvec->state = 0;

                /* Battery quirk - Often incomplete, and likes to crash */
                if (nvec->rx->data[0] == NVEC_BAT)
                        complete(&nvec->ec_transfer);

                return;
        }

        spin_lock(&nvec->rx_lock);

        /* add the received data to the work list
           and move the ring buffer pointer to the next entry */
        list_add_tail(&nvec->rx->node, &nvec->rx_data);

        spin_unlock(&nvec->rx_lock);

        nvec->state = 0;

        if (!nvec_msg_is_event(nvec->rx))
                complete(&nvec->ec_transfer);

        schedule_work(&nvec->rx_work);
}

/**
 * nvec_invalid_flags - Send an error message about invalid flags and jump
 * @nvec: The nvec device
 * @status: The status flags
 * @reset: Whether we shall jump to state 0.
 */
static void nvec_invalid_flags(struct nvec_chip *nvec, unsigned int status,
                               bool reset)
{
        dev_err(nvec->dev, "unexpected status flags 0x%02x during state %i\n",
                status, nvec->state);
        if (reset)
                nvec->state = 0;
}

/**
 * nvec_tx_set - Set the message to transfer (nvec->tx)
 * @nvec: A &struct nvec_chip
 *
 * Gets the first entry from the tx_data list of @nvec and sets the
 * tx member to it. If the tx_data list is empty, this uses the
 * tx_scratch message to send a no operation message.
 */
static void nvec_tx_set(struct nvec_chip *nvec)
{
        spin_lock(&nvec->tx_lock);
        if (list_empty(&nvec->tx_data)) {
                dev_err(nvec->dev, "empty tx - sending no-op\n");
                memcpy(nvec->tx_scratch.data, "\x02\x07\x02", 3);
                nvec->tx_scratch.size = 3;
                nvec->tx_scratch.pos = 0;
                nvec->tx = &nvec->tx_scratch;
                list_add_tail(&nvec->tx->node, &nvec->tx_data);
        } else {
                nvec->tx = list_first_entry(&nvec->tx_data, struct nvec_msg,
                                            node);
                nvec->tx->pos = 0;
        }
        spin_unlock(&nvec->tx_lock);

        dev_dbg(nvec->dev, "Sending message of length %u, command 0x%x\n",
                (uint)nvec->tx->size, nvec->tx->data[1]);
}

/**
 * nvec_interrupt - Interrupt handler
 * @irq: The IRQ
 * @dev: The nvec device
 *
 * Interrupt handler that fills our RX buffers and empties our TX
 * buffers. This uses a finite state machine with ridiculous amounts
 * of error checking, in order to be fairly reliable.
 */
static irqreturn_t nvec_interrupt(int irq, void *dev)
{
        unsigned long status;
        unsigned int received = 0;
        unsigned char to_send = 0xff;
        const unsigned long irq_mask = I2C_SL_IRQ | END_TRANS | RCVD | RNW;
        struct nvec_chip *nvec = dev;
        unsigned int state = nvec->state;

        status = readl(nvec->base + I2C_SL_STATUS);

        /* Filter out some errors */
        if ((status & irq_mask) == 0 && (status & ~irq_mask) != 0) {
                dev_err(nvec->dev, "unexpected irq mask %lx\n", status);
                return IRQ_HANDLED;
        }
        if ((status & I2C_SL_IRQ) == 0) {
                dev_err(nvec->dev, "Spurious IRQ\n");
                return IRQ_HANDLED;
        }

        /* The EC did not request a read, so it send us something, read it */
        if ((status & RNW) == 0) {
                received = readl(nvec->base + I2C_SL_RCVD);
                if (status & RCVD)
                        writel(0, nvec->base + I2C_SL_RCVD);
        }

        if (status == (I2C_SL_IRQ | RCVD))
                nvec->state = 0;

        switch (nvec->state) {
        case 0:         /* Verify that its a transfer start, the rest later */
                if (status != (I2C_SL_IRQ | RCVD))
                        nvec_invalid_flags(nvec, status, false);
                break;
        case 1:         /* command byte */
                if (status != I2C_SL_IRQ) {
                        nvec_invalid_flags(nvec, status, true);
                } else {
                        nvec->rx = nvec_msg_alloc(nvec, NVEC_MSG_RX);
                        /* Should not happen in a normal world */
                        if (unlikely(nvec->rx == NULL)) {
                                nvec->state = 0;
                                break;
                        }
                        nvec->rx->data[0] = received;
                        nvec->rx->pos = 1;
                        nvec->state = 2;
                }
                break;
        case 2:         /* first byte after command */
                if (status == (I2C_SL_IRQ | RNW | RCVD)) {
                        udelay(33);
                        if (nvec->rx->data[0] != 0x01) {
                                dev_err(nvec->dev,
                                        "Read without prior read command\n");
                                nvec->state = 0;
                                break;
                        }
                        nvec_msg_free(nvec, nvec->rx);
                        nvec->state = 3;
                        nvec_tx_set(nvec);
                        BUG_ON(nvec->tx->size < 1);
                        to_send = nvec->tx->data[0];
                        nvec->tx->pos = 1;
                } else if (status == (I2C_SL_IRQ)) {
                        BUG_ON(nvec->rx == NULL);
                        nvec->rx->data[1] = received;
                        nvec->rx->pos = 2;
                        nvec->state = 4;
                } else {
                        nvec_invalid_flags(nvec, status, true);
                }
                break;
        case 3:         /* EC does a block read, we transmit data */
                if (status & END_TRANS) {
                        nvec_tx_completed(nvec);
                } else if ((status & RNW) == 0 || (status & RCVD)) {
                        nvec_invalid_flags(nvec, status, true);
                } else if (nvec->tx && nvec->tx->pos < nvec->tx->size) {
                        to_send = nvec->tx->data[nvec->tx->pos++];
                } else {
                        dev_err(nvec->dev, "tx buffer underflow on %p (%u > %u)\n",
                                nvec->tx,
                                (uint) (nvec->tx ? nvec->tx->pos : 0),
                                (uint) (nvec->tx ? nvec->tx->size : 0));
                        nvec->state = 0;
                }
                break;
        case 4:         /* EC does some write, we read the data */
                if ((status & (END_TRANS | RNW)) == END_TRANS)
                        nvec_rx_completed(nvec);
                else if (status & (RNW | RCVD))
                        nvec_invalid_flags(nvec, status, true);
                else if (nvec->rx && nvec->rx->pos < NVEC_MSG_SIZE)
                        nvec->rx->data[nvec->rx->pos++] = received;
                else
                        dev_err(nvec->dev,
                                "RX buffer overflow on %p: "
                                "Trying to write byte %u of %u\n",
                                nvec->rx, nvec->rx ? nvec->rx->pos : 0,
                                NVEC_MSG_SIZE);
                break;
        default:
                nvec->state = 0;
        }

        /* If we are told that a new transfer starts, verify it */
        if ((status & (RCVD | RNW)) == RCVD) {
                if (received != nvec->i2c_addr)
                        dev_err(nvec->dev,
                        "received address 0x%02x, expected 0x%02x\n",
                        received, nvec->i2c_addr);
                nvec->state = 1;
        }

        /* Send data if requested, but not on end of transmission */
        if ((status & (RNW | END_TRANS)) == RNW)
                writel(to_send, nvec->base + I2C_SL_RCVD);

        /* If we have send the first byte */
        if (status == (I2C_SL_IRQ | RNW | RCVD))
                nvec_gpio_set_value(nvec, 1);

        dev_dbg(nvec->dev,
                "Handled: %s 0x%02x, %s 0x%02x in state %u [%s%s%s]\n",
                (status & RNW) == 0 ? "received" : "R=",
                received,
                (status & (RNW | END_TRANS)) ? "sent" : "S=",
                to_send,
                state,
                status & END_TRANS ? " END_TRANS" : "",
                status & RCVD ? " RCVD" : "",
                status & RNW ? " RNW" : "");


        /*
         * TODO: A correct fix needs to be found for this.
         *
         * We experience less incomplete messages with this delay than without
         * it, but we don't know why. Help is appreciated.
         */
        udelay(100);

        return IRQ_HANDLED;
}

static void tegra_init_i2c_slave(struct nvec_chip *nvec)
{
        u32 val;

        clk_prepare_enable(nvec->i2c_clk);

        tegra_periph_reset_assert(nvec->i2c_clk);
        udelay(2);
        tegra_periph_reset_deassert(nvec->i2c_clk);

        val = I2C_CNFG_NEW_MASTER_SFM | I2C_CNFG_PACKET_MODE_EN |
            (0x2 << I2C_CNFG_DEBOUNCE_CNT_SHIFT);
        writel(val, nvec->base + I2C_CNFG);

        clk_set_rate(nvec->i2c_clk, 8 * 80000);

        writel(I2C_SL_NEWSL, nvec->base + I2C_SL_CNFG);
        writel(0x1E, nvec->base + I2C_SL_DELAY_COUNT);

        writel(nvec->i2c_addr>>1, nvec->base + I2C_SL_ADDR1);
        writel(0, nvec->base + I2C_SL_ADDR2);

        enable_irq(nvec->irq);
}

#ifdef CONFIG_PM_SLEEP
static void nvec_disable_i2c_slave(struct nvec_chip *nvec)
{
        disable_irq(nvec->irq);
        writel(I2C_SL_NEWSL | I2C_SL_NACK, nvec->base + I2C_SL_CNFG);
        clk_disable_unprepare(nvec->i2c_clk);
}
#endif

static void nvec_power_off(void)
{
        char ap_pwr_down[] = { NVEC_SLEEP, AP_PWR_DOWN };

        nvec_toggle_global_events(nvec_power_handle, false);
        nvec_write_async(nvec_power_handle, ap_pwr_down, 2);
}

/*
 *  Parse common device tree data
 */
static int nvec_i2c_parse_dt_pdata(struct nvec_chip *nvec)
{
        nvec->gpio = of_get_named_gpio(nvec->dev->of_node, "request-gpios", 0);

        if (nvec->gpio < 0) {
                dev_err(nvec->dev, "no gpio specified");
                return -ENODEV;
        }

        if (of_property_read_u32(nvec->dev->of_node, "slave-addr",
                                &nvec->i2c_addr)) {
                dev_err(nvec->dev, "no i2c address specified");
                return -ENODEV;
        }

        return 0;
}

static int tegra_nvec_probe(struct platform_device *pdev)
{
        int err, ret;
        struct clk *i2c_clk;
        struct nvec_chip *nvec;
        struct nvec_msg *msg;
        struct resource *res;
        void __iomem *base;
        char    get_firmware_version[] = { NVEC_CNTL, GET_FIRMWARE_VERSION },
                unmute_speakers[] = { NVEC_OEM0, 0x10, 0x59, 0x95 },
                enable_event[7] = { NVEC_SYS, CNF_EVENT_REPORTING, true };

        if (!pdev->dev.of_node) {
                dev_err(&pdev->dev, "must be instantiated using device tree\n");
                return -ENODEV;
        }

        nvec = devm_kzalloc(&pdev->dev, sizeof(struct nvec_chip), GFP_KERNEL);
        if (nvec == NULL) {
                dev_err(&pdev->dev, "failed to reserve memory\n");
                return -ENOMEM;
        }
        platform_set_drvdata(pdev, nvec);
        nvec->dev = &pdev->dev;

        err = nvec_i2c_parse_dt_pdata(nvec);
        if (err < 0)
                return err;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(base))
                return PTR_ERR(base);

        res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (!res) {
                dev_err(&pdev->dev, "no irq resource?\n");
                return -ENODEV;
        }

        i2c_clk = devm_clk_get(&pdev->dev, "div-clk");
        if (IS_ERR(i2c_clk)) {
                dev_err(nvec->dev, "failed to get controller clock\n");
                return -ENODEV;
        }

        nvec->base = base;
        nvec->irq = res->start;
        nvec->i2c_clk = i2c_clk;
        nvec->rx = &nvec->msg_pool[0];

        ATOMIC_INIT_NOTIFIER_HEAD(&nvec->notifier_list);

        init_completion(&nvec->sync_write);
        init_completion(&nvec->ec_transfer);
        mutex_init(&nvec->sync_write_mutex);
        spin_lock_init(&nvec->tx_lock);
        spin_lock_init(&nvec->rx_lock);
        INIT_LIST_HEAD(&nvec->rx_data);
        INIT_LIST_HEAD(&nvec->tx_data);
        INIT_WORK(&nvec->rx_work, nvec_dispatch);
        INIT_WORK(&nvec->tx_work, nvec_request_master);

        err = devm_gpio_request_one(&pdev->dev, nvec->gpio, GPIOF_OUT_INIT_HIGH,
                                        "nvec gpio");
        if (err < 0) {
                dev_err(nvec->dev, "couldn't request gpio\n");
                return -ENODEV;
        }

        err = devm_request_irq(&pdev->dev, nvec->irq, nvec_interrupt, 0,
                                "nvec", nvec);
        if (err) {
                dev_err(nvec->dev, "couldn't request irq\n");
                return -ENODEV;
        }
        disable_irq(nvec->irq);

        tegra_init_i2c_slave(nvec);

        /* enable event reporting */
        nvec_toggle_global_events(nvec, true);

        nvec->nvec_status_notifier.notifier_call = nvec_status_notifier;
        nvec_register_notifier(nvec, &nvec->nvec_status_notifier, 0);

        nvec_power_handle = nvec;
        pm_power_off = nvec_power_off;

        /* Get Firmware Version */
        msg = nvec_write_sync(nvec, get_firmware_version, 2);

        if (msg) {
                dev_warn(nvec->dev, "ec firmware version %02x.%02x.%02x / %02x\n",
                        msg->data[4], msg->data[5], msg->data[6], msg->data[7]);

                nvec_msg_free(nvec, msg);
        }

        ret = mfd_add_devices(nvec->dev, -1, nvec_devices,
                              ARRAY_SIZE(nvec_devices), base, 0, NULL);
        if (ret)
                dev_err(nvec->dev, "error adding subdevices\n");

        /* unmute speakers? */
        nvec_write_async(nvec, unmute_speakers, 4);

        /* enable lid switch event */
        nvec_event_mask(enable_event, LID_SWITCH);
        nvec_write_async(nvec, enable_event, 7);

        /* enable power button event */
        nvec_event_mask(enable_event, PWR_BUTTON);
        nvec_write_async(nvec, enable_event, 7);

        return 0;
}

static int tegra_nvec_remove(struct platform_device *pdev)
{
        struct nvec_chip *nvec = platform_get_drvdata(pdev);

        nvec_toggle_global_events(nvec, false);
        mfd_remove_devices(nvec->dev);
        nvec_unregister_notifier(nvec, &nvec->nvec_status_notifier);
        cancel_work_sync(&nvec->rx_work);
        cancel_work_sync(&nvec->tx_work);
        /* FIXME: needs check wether nvec is responsible for power off */
        pm_power_off = NULL;

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int nvec_suspend(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct nvec_chip *nvec = platform_get_drvdata(pdev);
        struct nvec_msg *msg;
        char ap_suspend[] = { NVEC_SLEEP, AP_SUSPEND };

        dev_dbg(nvec->dev, "suspending\n");

        /* keep these sync or you'll break suspend */
        nvec_toggle_global_events(nvec, false);

        msg = nvec_write_sync(nvec, ap_suspend, sizeof(ap_suspend));
        nvec_msg_free(nvec, msg);

        nvec_disable_i2c_slave(nvec);

        return 0;
}

static int nvec_resume(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct nvec_chip *nvec = platform_get_drvdata(pdev);

        dev_dbg(nvec->dev, "resuming\n");
        tegra_init_i2c_slave(nvec);
        nvec_toggle_global_events(nvec, true);

        return 0;
}
#endif

static const SIMPLE_DEV_PM_OPS(nvec_pm_ops, nvec_suspend, nvec_resume);

/* Match table for of_platform binding */
static const struct of_device_id nvidia_nvec_of_match[] = {
        { .compatible = "nvidia,nvec", },
        {},
};
MODULE_DEVICE_TABLE(of, nvidia_nvec_of_match);

static struct platform_driver nvec_device_driver = {
        .probe   = tegra_nvec_probe,
        .remove  = tegra_nvec_remove,
        .driver  = {
                .name = "nvec",
                .owner = THIS_MODULE,
                .pm = &nvec_pm_ops,
                .of_match_table = nvidia_nvec_of_match,
        }
};

module_platform_driver(nvec_device_driver);

MODULE_ALIAS("platform:nvec");
MODULE_DESCRIPTION("NVIDIA compliant embedded controller interface");
MODULE_AUTHOR("Marc Dietrich <marvin24@gmx.de>");
MODULE_LICENSE("GPL");