On Wed, Dec 16, 2020 at 07:14:25PM +0200, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Tue, Dec 15, 2020 at 06:09:56PM +0100, Jacopo Mondi wrote:
> > 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@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> > ---
> > 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 1cfc8801c0b2..021309c6dd6f 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;
>
> This could also be written
>
> chan_amplitude = min(30, chan_amplitude - 100);
s/min/max/ of course.
>
> With or without the change,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>
> > + 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
--
Regards,
Laurent Pinchart
