From 5a386b1ff7710dec76c586a3e79f862fc9fc9d73 Mon Sep 17 00:00:00 2001 From: Jacopo Mondi Date: Thu, 14 Jan 2021 18:04:28 +0100 Subject: media: i2c: max9286: Make channel amplitude programmable 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 Reviewed-by: Kieran Bingham Signed-off-by: Jacopo Mondi Signed-off-by: Sakari Ailus Signed-off-by: Mauro Carvalho Chehab --- drivers/media/i2c/max9286.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) (limited to 'drivers/media') diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c index ebe9c2215b48..4d7587dfb5aa 100644 --- a/drivers/media/i2c/max9286.c +++ b/drivers/media/i2c/max9286.c @@ -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 -- cgit v1.2.3