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    Subject[PATCH v3 6/9] drm/i915: Make use of indexed write GMBUS feature
    Date
    This patch enables the indexed write feature of the GMBUS to concatenate
    2 consecutive messages into one. The criteria for an indexed write is
    that both messages are writes, the first is length == 1, and the second
    is length > 0. The first message is sent out by the GMBUS as the slave
    command, and the second one is sent via the GMBUS FIFO as usual.

    Changes in v3:
    - Added to series

    Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Signed-off-by: Sean Paul <seanpaul@chromium.org>
    ---
    drivers/gpu/drm/i915/intel_i2c.c | 39 ++++++++++++++++++++++++++++++++++-----
    1 file changed, 34 insertions(+), 5 deletions(-)

    diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
    index 49fdf09f9919..7399009aee0a 100644
    --- a/drivers/gpu/drm/i915/intel_i2c.c
    +++ b/drivers/gpu/drm/i915/intel_i2c.c
    @@ -373,7 +373,8 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg,

    static int
    gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,
    - unsigned short addr, u8 *buf, unsigned int len)
    + unsigned short addr, u8 *buf, unsigned int len,
    + u32 gmbus1_index)
    {
    unsigned int chunk_size = len;
    u32 val, loop;
    @@ -386,7 +387,7 @@ gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,

    I915_WRITE_FW(GMBUS3, val);
    I915_WRITE_FW(GMBUS1,
    - GMBUS_CYCLE_WAIT |
    + gmbus1_index | GMBUS_CYCLE_WAIT |
    (chunk_size << GMBUS_BYTE_COUNT_SHIFT) |
    (addr << GMBUS_SLAVE_ADDR_SHIFT) |
    GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
    @@ -409,7 +410,8 @@ gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,
    }

    static int
    -gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
    +gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
    + u32 gmbus1_index)
    {
    u8 *buf = msg->buf;
    unsigned int tx_size = msg->len;
    @@ -419,7 +421,8 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
    do {
    len = min(tx_size, GMBUS_BYTE_COUNT_MAX);

    - ret = gmbus_xfer_write_chunk(dev_priv, msg->addr, buf, len);
    + ret = gmbus_xfer_write_chunk(dev_priv, msg->addr, buf, len,
    + gmbus1_index);
    if (ret)
    return ret;

    @@ -430,6 +433,14 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg)
    return 0;
    }

    +static int
    +gmbus_xfer_index_write(struct drm_i915_private *dev_priv, u8 cmd,
    + struct i2c_msg *msg)
    +{
    + u8 gmbus1_index = GMBUS_CYCLE_INDEX | (cmd << GMBUS_SLAVE_INDEX_SHIFT);
    + return gmbus_xfer_write(dev_priv, msg, gmbus1_index);
    +}
    +
    /*
    * The gmbus controller can combine a 1 or 2 byte write with a read that
    * immediately follows it by using an "INDEX" cycle.
    @@ -444,6 +455,20 @@ gmbus_is_index_read(struct i2c_msg *msgs, int i, int num)
    (msgs[i + 1].flags & I2C_M_RD));
    }

    +/*
    + * The gmbus controller can combine a 2-msg write into a single write that
    + * immediately follows it by using an "INDEX" cycle.
    + */
    +static bool
    +gmbus_is_index_write(struct i2c_msg *msgs, int i, int num)
    +{
    + return (i + 1 < num &&
    + msgs[i].addr == msgs[i + 1].addr &&
    + !(msgs[i].flags & I2C_M_RD) &&
    + !(msgs[i + 1].flags & I2C_M_RD) &&
    + (msgs[i].len == 1 || msgs[i + 1].len > 0));
    +}
    +
    static int
    gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)
    {
    @@ -489,10 +514,14 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
    if (gmbus_is_index_read(msgs, i, num)) {
    ret = gmbus_xfer_index_read(dev_priv, &msgs[i]);
    inc = 2; /* an index read is two msgs */
    + } else if (gmbus_is_index_write(msgs, i, num)) {
    + ret = gmbus_xfer_index_write(dev_priv, msgs[i].buf[0],
    + &msgs[i + 1]);
    + inc = 2; /* an index write is two msgs */
    } 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]);
    + ret = gmbus_xfer_write(dev_priv, &msgs[i], 0);
    }

    if (!ret)
    --
    2.15.0.531.g2ccb3012c9-goog
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