intel_i2c.c

Go to the documentation of this file.

/*
 * Copyright (c) 2006 Dave Airlie <[email protected]>
 * Copyright © 2006-2008,2010 Intel Corporation
 *   Jesse Barnes <[email protected]>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Authors:
 *  Eric Anholt <[email protected]>
 *  Chris Wilson <[email protected]>
 */
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <linux/export.h>
#include <drm/drmP.h>
#include "intel_drv.h"
#include <drm/i915_drm.h>
#include "i915_drv.h"

struct gmbus_port {
    const char *name;
    int reg;
};

static const struct gmbus_port gmbus_ports[] = {
    { "ssc", GPIOB },
    { "vga", GPIOA },
    { "panel", GPIOC },
    { "dpc", GPIOD },
    { "dpb", GPIOE },
    { "dpd", GPIOF },
};

/* Intel GPIO access functions */

#define I2C_RISEFALL_TIME 10

static inline struct intel_gmbus *
to_intel_gmbus(struct i2c_adapter *i2c)
{
    return container_of(i2c, struct intel_gmbus, adapter);
}

void
intel_i2c_reset(struct drm_device *dev)
{
    struct drm_i915_private *dev_priv = dev->dev_private;
    I915_WRITE(dev_priv->gpio_mmio_base + GMBUS0, 0);
}

static void intel_i2c_quirk_set(struct drm_i915_private *dev_priv, bool enable)
{
    u32 val;

    /* When using bit bashing for I2C, this bit needs to be set to 1 */
    if (!IS_PINEVIEW(dev_priv->dev))
        return;

    val = I915_READ(DSPCLK_GATE_D);
    if (enable)
        val |= DPCUNIT_CLOCK_GATE_DISABLE;
    else
        val &= ~DPCUNIT_CLOCK_GATE_DISABLE;
    I915_WRITE(DSPCLK_GATE_D, val);
}

static u32 get_reserved(struct intel_gmbus *bus)
{
    struct drm_i915_private *dev_priv = bus->dev_priv;
    struct drm_device *dev = dev_priv->dev;
    u32 reserved = 0;

    /* On most chips, these bits must be preserved in software. */
    if (!IS_I830(dev) && !IS_845G(dev))
        reserved = I915_READ_NOTRACE(bus->gpio_reg) &
                         (GPIO_DATA_PULLUP_DISABLE |
                          GPIO_CLOCK_PULLUP_DISABLE);

    return reserved;
}

static int get_clock(void *data)
{
    struct intel_gmbus *bus = data;
    struct drm_i915_private *dev_priv = bus->dev_priv;
    u32 reserved = get_reserved(bus);
    I915_WRITE_NOTRACE(bus->gpio_reg, reserved | GPIO_CLOCK_DIR_MASK);
    I915_WRITE_NOTRACE(bus->gpio_reg, reserved);
    return (I915_READ_NOTRACE(bus->gpio_reg) & GPIO_CLOCK_VAL_IN) != 0;
}

static int get_data(void *data)
{
    struct intel_gmbus *bus = data;
    struct drm_i915_private *dev_priv = bus->dev_priv;
    u32 reserved = get_reserved(bus);
    I915_WRITE_NOTRACE(bus->gpio_reg, reserved | GPIO_DATA_DIR_MASK);
    I915_WRITE_NOTRACE(bus->gpio_reg, reserved);
    return (I915_READ_NOTRACE(bus->gpio_reg) & GPIO_DATA_VAL_IN) != 0;
}

static void set_clock(void *data, int state_high)
{
    struct intel_gmbus *bus = data;
    struct drm_i915_private *dev_priv = bus->dev_priv;
    u32 reserved = get_reserved(bus);
    u32 clock_bits;

    if (state_high)
        clock_bits = GPIO_CLOCK_DIR_IN | GPIO_CLOCK_DIR_MASK;
    else
        clock_bits = GPIO_CLOCK_DIR_OUT | GPIO_CLOCK_DIR_MASK |
            GPIO_CLOCK_VAL_MASK;

    I915_WRITE_NOTRACE(bus->gpio_reg, reserved | clock_bits);
    POSTING_READ(bus->gpio_reg);
}

static void set_data(void *data, int state_high)
{
    struct intel_gmbus *bus = data;
    struct drm_i915_private *dev_priv = bus->dev_priv;
    u32 reserved = get_reserved(bus);
    u32 data_bits;

    if (state_high)
        data_bits = GPIO_DATA_DIR_IN | GPIO_DATA_DIR_MASK;
    else
        data_bits = GPIO_DATA_DIR_OUT | GPIO_DATA_DIR_MASK |
            GPIO_DATA_VAL_MASK;

    I915_WRITE_NOTRACE(bus->gpio_reg, reserved | data_bits);
    POSTING_READ(bus->gpio_reg);
}

static int
intel_gpio_pre_xfer(struct i2c_adapter *adapter)
{
    struct intel_gmbus *bus = container_of(adapter,
                           struct intel_gmbus,
                           adapter);
    struct drm_i915_private *dev_priv = bus->dev_priv;

    intel_i2c_reset(dev_priv->dev);
    intel_i2c_quirk_set(dev_priv, true);
    set_data(bus, 1);
    set_clock(bus, 1);
    udelay(I2C_RISEFALL_TIME);
    return 0;
}

static void
intel_gpio_post_xfer(struct i2c_adapter *adapter)
{
    struct intel_gmbus *bus = container_of(adapter,
                           struct intel_gmbus,
                           adapter);
    struct drm_i915_private *dev_priv = bus->dev_priv;

    set_data(bus, 1);
    set_clock(bus, 1);
    intel_i2c_quirk_set(dev_priv, false);
}

static void
intel_gpio_setup(struct intel_gmbus *bus, u32 pin)
{
    struct drm_i915_private *dev_priv = bus->dev_priv;
    struct i2c_algo_bit_data *algo;

    algo = &bus->bit_algo;

    /* -1 to map pin pair to gmbus index */
    bus->gpio_reg = dev_priv->gpio_mmio_base + gmbus_ports[pin - 1].reg;

    bus->adapter.algo_data = algo;
    algo->setsda = set_data;
    algo->setscl = set_clock;
    algo->getsda = get_data;
    algo->getscl = get_clock;
    algo->pre_xfer = intel_gpio_pre_xfer;
    algo->post_xfer = intel_gpio_post_xfer;
    algo->udelay = I2C_RISEFALL_TIME;
    algo->timeout = usecs_to_jiffies(2200);
    algo->data = bus;
}

static int
gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
        u32 gmbus1_index)
{
    int reg_offset = dev_priv->gpio_mmio_base;
    u16 len = msg->len;
    u8 *buf = msg->buf;

    I915_WRITE(GMBUS1 + reg_offset,
           gmbus1_index |
           GMBUS_CYCLE_WAIT |
           (len << GMBUS_BYTE_COUNT_SHIFT) |
           (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) |
           GMBUS_SLAVE_READ | GMBUS_SW_RDY);
    while (len) {
        int ret;
        u32 val, loop = 0;
        u32 gmbus2;

        ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
                   (GMBUS_SATOER | GMBUS_HW_RDY),
                   50);
        if (ret)
            return -ETIMEDOUT;
        if (gmbus2 & GMBUS_SATOER)
            return -ENXIO;

        val = I915_READ(GMBUS3 + reg_offset);
        do {
            *buf++ = val & 0xff;
            val >>= 8;
        } while (--len && ++loop < 4);
    }

    return 0;
}

static int
gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
{
    int reg_offset = dev_priv->gpio_mmio_base;
    u16 len = msg->len;
    u8 *buf = msg->buf;
    u32 val, loop;

    val = loop = 0;
    while (len && loop < 4) {
        val |= *buf++ << (8 * loop++);
        len -= 1;
    }

    I915_WRITE(GMBUS3 + reg_offset, val);
    I915_WRITE(GMBUS1 + reg_offset,
           GMBUS_CYCLE_WAIT |
           (msg->len << GMBUS_BYTE_COUNT_SHIFT) |
           (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) |
           GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
    while (len) {
        int ret;
        u32 gmbus2;

        val = loop = 0;
        do {
            val |= *buf++ << (8 * loop);
        } while (--len && ++loop < 4);

        I915_WRITE(GMBUS3 + reg_offset, val);

        ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
                   (GMBUS_SATOER | GMBUS_HW_RDY),
                   50);
        if (ret)
            return -ETIMEDOUT;
        if (gmbus2 & GMBUS_SATOER)
            return -ENXIO;
    }
    return 0;
}

/*
 * The gmbus controller can combine a 1 or 2 byte write with a read that
 * immediately follows it by using an "INDEX" cycle.
 */
static bool
gmbus_is_index_read(struct i2c_msg *msgs, int i, int num)
{
    return (i + 1 < num &&
        !(msgs[i].flags & I2C_M_RD) && msgs[i].len <= 2 &&
        (msgs[i + 1].flags & I2C_M_RD));
}

static int
gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)
{
    int reg_offset = dev_priv->gpio_mmio_base;
    u32 gmbus1_index = 0;
    u32 gmbus5 = 0;
    int ret;

    if (msgs[0].len == 2)
        gmbus5 = GMBUS_2BYTE_INDEX_EN |
             msgs[0].buf[1] | (msgs[0].buf[0] << 8);
    if (msgs[0].len == 1)
        gmbus1_index = GMBUS_CYCLE_INDEX |
                   (msgs[0].buf[0] << GMBUS_SLAVE_INDEX_SHIFT);

    /* GMBUS5 holds 16-bit index */
    if (gmbus5)
        I915_WRITE(GMBUS5 + reg_offset, gmbus5);

    ret = gmbus_xfer_read(dev_priv, &msgs[1], gmbus1_index);

    /* Clear GMBUS5 after each index transfer */
    if (gmbus5)
        I915_WRITE(GMBUS5 + reg_offset, 0);

    return ret;
}

static int
gmbus_xfer(struct i2c_adapter *adapter,
       struct i2c_msg *msgs,
       int num)
{
    struct intel_gmbus *bus = container_of(adapter,
                           struct intel_gmbus,
                           adapter);
    struct drm_i915_private *dev_priv = bus->dev_priv;
    int i, reg_offset;
    int ret = 0;

    mutex_lock(&dev_priv->gmbus_mutex);

    if (bus->force_bit) {
        ret = i2c_bit_algo.master_xfer(adapter, msgs, num);
        goto out;
    }

    reg_offset = dev_priv->gpio_mmio_base;

    I915_WRITE(GMBUS0 + reg_offset, bus->reg0);

    for (i = 0; i < num; i++) {
        u32 gmbus2;

        if (gmbus_is_index_read(msgs, i, num)) {
            ret = gmbus_xfer_index_read(dev_priv, &msgs[i]);
            i += 1;  /* set i to the index of the read xfer */
        } else if (msgs[i].flags & I2C_M_RD) {
            ret = gmbus_xfer_read(dev_priv, &msgs[i], 0);
        } else {
            ret = gmbus_xfer_write(dev_priv, &msgs[i]);
        }

        if (ret == -ETIMEDOUT)
            goto timeout;
        if (ret == -ENXIO)
            goto clear_err;

        ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
                   (GMBUS_SATOER | GMBUS_HW_WAIT_PHASE),
                   50);
        if (ret)
            goto timeout;
        if (gmbus2 & GMBUS_SATOER)
            goto clear_err;
    }

    /* Generate a STOP condition on the bus. Note that gmbus can't generata
     * a STOP on the very first cycle. To simplify the code we
     * unconditionally generate the STOP condition with an additional gmbus
     * cycle. */
    I915_WRITE(GMBUS1 + reg_offset, GMBUS_CYCLE_STOP | GMBUS_SW_RDY);

    /* Mark the GMBUS interface as disabled after waiting for idle.
     * We will re-enable it at the start of the next xfer,
     * till then let it sleep.
     */
    if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
             10)) {
        DRM_DEBUG_KMS("GMBUS [%s] timed out waiting for idle\n",
             adapter->name);
        ret = -ETIMEDOUT;
    }
    I915_WRITE(GMBUS0 + reg_offset, 0);
    ret = ret ?: i;
    goto out;

clear_err:
    /*
     * Wait for bus to IDLE before clearing NAK.
     * If we clear the NAK while bus is still active, then it will stay
     * active and the next transaction may fail.
     *
     * If no ACK is received during the address phase of a transaction, the
     * adapter must report -ENXIO. It is not clear what to return if no ACK
     * is received at other times. But we have to be careful to not return
     * spurious -ENXIO because that will prevent i2c and drm edid functions
     * from retrying. So return -ENXIO only when gmbus properly quiescents -
     * timing out seems to happen when there _is_ a ddc chip present, but
     * it's slow responding and only answers on the 2nd retry.
     */
    ret = -ENXIO;
    if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0,
             10)) {
        DRM_DEBUG_KMS("GMBUS [%s] timed out after NAK\n",
                  adapter->name);
        ret = -ETIMEDOUT;
    }

    /* Toggle the Software Clear Interrupt bit. This has the effect
     * of resetting the GMBUS controller and so clearing the
     * BUS_ERROR raised by the slave's NAK.
     */
    I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT);
    I915_WRITE(GMBUS1 + reg_offset, 0);
    I915_WRITE(GMBUS0 + reg_offset, 0);

    DRM_DEBUG_KMS("GMBUS [%s] NAK for addr: %04x %c(%d)\n",
             adapter->name, msgs[i].addr,
             (msgs[i].flags & I2C_M_RD) ? 'r' : 'w', msgs[i].len);

    goto out;

timeout:
    DRM_INFO("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
         bus->adapter.name, bus->reg0 & 0xff);
    I915_WRITE(GMBUS0 + reg_offset, 0);

    /* Hardware may not support GMBUS over these pins? Try GPIO bitbanging instead. */
    bus->force_bit = true;
    ret = i2c_bit_algo.master_xfer(adapter, msgs, num);

out:
    mutex_unlock(&dev_priv->gmbus_mutex);
    return ret;
}

static u32 gmbus_func(struct i2c_adapter *adapter)
{
    return i2c_bit_algo.functionality(adapter) &
        (I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
        /* I2C_FUNC_10BIT_ADDR | */
        I2C_FUNC_SMBUS_READ_BLOCK_DATA |
        I2C_FUNC_SMBUS_BLOCK_PROC_CALL);
}

static const struct i2c_algorithm gmbus_algorithm = {
    .master_xfer    = gmbus_xfer,
    .functionality  = gmbus_func
};

int intel_setup_gmbus(struct drm_device *dev)
{
    struct drm_i915_private *dev_priv = dev->dev_private;
    int ret, i;

    if (HAS_PCH_SPLIT(dev))
        dev_priv->gpio_mmio_base = PCH_GPIOA - GPIOA;
    else
        dev_priv->gpio_mmio_base = 0;

    mutex_init(&dev_priv->gmbus_mutex);

    for (i = 0; i < GMBUS_NUM_PORTS; i++) {
        struct intel_gmbus *bus = &dev_priv->gmbus[i];
        u32 port = i + 1; /* +1 to map gmbus index to pin pair */

        bus->adapter.owner = THIS_MODULE;
        bus->adapter.class = I2C_CLASS_DDC;
        snprintf(bus->adapter.name,
             sizeof(bus->adapter.name),
             "i915 gmbus %s",
             gmbus_ports[i].name);

        bus->adapter.dev.parent = &dev->pdev->dev;
        bus->dev_priv = dev_priv;

        bus->adapter.algo = &gmbus_algorithm;

        /* By default use a conservative clock rate */
        bus->reg0 = port | GMBUS_RATE_100KHZ;

        /* gmbus seems to be broken on i830 */
        if (IS_I830(dev))
            bus->force_bit = true;

        intel_gpio_setup(bus, port);

        ret = i2c_add_adapter(&bus->adapter);
        if (ret)
            goto err;
    }

    intel_i2c_reset(dev_priv->dev);

    return 0;

err:
    while (--i) {
        struct intel_gmbus *bus = &dev_priv->gmbus[i];
        i2c_del_adapter(&bus->adapter);
    }
    return ret;
}

struct i2c_adapter *intel_gmbus_get_adapter(struct drm_i915_private *dev_priv,
                        unsigned port)
{
    WARN_ON(!intel_gmbus_is_port_valid(port));
    /* -1 to map pin pair to gmbus index */
    return (intel_gmbus_is_port_valid(port)) ?
        &dev_priv->gmbus[port - 1].adapter : NULL;
}

void intel_gmbus_set_speed(struct i2c_adapter *adapter, int speed)
{
    struct intel_gmbus *bus = to_intel_gmbus(adapter);

    bus->reg0 = (bus->reg0 & ~(0x3 << 8)) | speed;
}

void intel_gmbus_force_bit(struct i2c_adapter *adapter, bool force_bit)
{
    struct intel_gmbus *bus = to_intel_gmbus(adapter);

    bus->force_bit = force_bit;
}

void intel_teardown_gmbus(struct drm_device *dev)
{
    struct drm_i915_private *dev_priv = dev->dev_private;
    int i;

    for (i = 0; i < GMBUS_NUM_PORTS; i++) {
        struct intel_gmbus *bus = &dev_priv->gmbus[i];
        i2c_del_adapter(&bus->adapter);
    }
}