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media: i2c: max9286: Make channel amplitude programmable

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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: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Jacopo Mondi 2021-01-14 18:04:28 +01:00 committed by Mauro Carvalho Chehab
parent 02b57eb3b5
commit 5a386b1ff7
1 changed files with 15 additions and 6 deletions
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21
drivers/media/i2c/max9286.c
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@ -336,19 +336,28 @@ 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 = max(30U, 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 +966,7 @@ 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