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    Subject[PATCH v3 4/7] media: i2c: max9286: Make channel amplitude programmable
    Date
    Instrument the function that configures the reverse channel with a
    programmable amplitude value.

    This change serves to prepare to adjust the reverse channel amplitude
    depending on the remote end high-threshold configuration.

    Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
    Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
    ---
    drivers/media/i2c/max9286.c | 22 ++++++++++++++++------
    1 file changed, 16 insertions(+), 6 deletions(-)

    diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
    index 526b6e557dfb..31e27d0f34f1 100644
    --- a/drivers/media/i2c/max9286.c
    +++ b/drivers/media/i2c/max9286.c
    @@ -336,19 +336,29 @@ static void max9286_configure_i2c(struct max9286_priv *priv, bool localack)
    usleep_range(3000, 5000);
    }

    -static void max9286_reverse_channel_setup(struct max9286_priv *priv)
    +static void max9286_reverse_channel_setup(struct max9286_priv *priv,
    + unsigned int chan_amplitude)
    {
    + /* Reverse channel transmission time: default to 1. */
    + u8 chan_config = MAX9286_REV_TRF(1);
    +
    /*
    * Reverse channel setup.
    *
    * - Enable custom reverse channel configuration (through register 0x3f)
    * and set the first pulse length to 35 clock cycles.
    - * - Increase the reverse channel amplitude to 170mV to accommodate the
    - * high threshold enabled by the serializer driver.
    + * - Adjust reverse channel amplitude: values > 130 are programmed
    + * using the additional +100mV REV_AMP_X boost flag
    */
    max9286_write(priv, 0x3f, MAX9286_EN_REV_CFG | MAX9286_REV_FLEN(35));
    - max9286_write(priv, 0x3b, MAX9286_REV_TRF(1) | MAX9286_REV_AMP(70) |
    - MAX9286_REV_AMP_X);
    +
    + if (chan_amplitude > 100) {
    + /* It is not possible to express values (100 < x < 130) */
    + chan_amplitude = chan_amplitude < 130
    + ? 30 : chan_amplitude - 100;
    + chan_config |= MAX9286_REV_AMP_X;
    + }
    + max9286_write(priv, 0x3b, chan_config | MAX9286_REV_AMP(chan_amplitude));
    usleep_range(2000, 2500);
    }

    @@ -957,7 +967,7 @@ static int max9286_setup(struct max9286_priv *priv)
    * only. This should be disabled after the mux is initialised.
    */
    max9286_configure_i2c(priv, true);
    - max9286_reverse_channel_setup(priv);
    + max9286_reverse_channel_setup(priv, 170);

    /*
    * Enable GMSL links, mask unused ones and autodetect link
    --
    2.28.0
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