[PATCH v8 3/6] drm/bridge: simple: Add the Lontium LT8711UXD DP-to-HDMI bridge

[Dmitry Baryshkov]

On Sat, Apr 25, 2026 at 01:10:02PM -0500, Dennis Gilmore wrote:
> On Sat, Apr 25, 2026 at 9:24 AM Dmitry Baryshkov
> <dmitry.baryshkov at oss.qualcomm.com> wrote:
> >
> > On Sat, Apr 25, 2026 at 02:28:44PM +0300, Laurent Pinchart wrote:
> > > Hi Dennis,
> > >
> > > Thank you for the patch.
> > >
> > > On Fri, Apr 24, 2026 at 10:10:08PM -0500, Dennis Gilmore wrote:
> > > > The Lontium LT8711UXD is a high performance two lane Type-C/DP1.4
> > > > to HDMI2.0 converter, designed to connect a USB Type-C source or
> > > > a DP1.4 source to an HDMI2.0 sink.
> > >
> > > As far as I can tell, the LT8711UXD has an I2C control interface.
> > > Shouldn't it be an I2C device ?
> >
> > From the datasheet:
> >
> > The device is capable of automatic operation which is
> > enabled by an integrated microprocessor that uses an
> > embedded SPI flash for firmware storage. System control
> > is also available through the use of a dedicated
> > configuration I2C slave interface.
> >
> > My guess was that it can either be an I2C device or it can function as a
> > simple platdev with no I2C controls. Please correct me if my
> > understanding was wrong.
> >
> > But now looking at the schematics, it seems to be connected to I2C6.
> > Which means that it should be desribed (and bound) as such.
> 
> Hi Dmitry and Laurent,
> 
> While the schematic shows that it can use I2C and has been wired up,
> it also shows that both MODE_SEL and I2C_ADDR have unpopulated 10k
> resistors; as a result, MODE_SEL is connected directly to GND, putting
> the bridge in autonomous mode. I confirmed this by running `i2cdetect
> -r -y 6`, with the only device on the bus being the HYM8563 RTC at
> 0x51. Without reworking the board, the device is not directly
> controllable and just runs autonomously.

I think it would be nice to mention:
- In the commit for the bindings, that the device can be running
  uncontrolled or it can be attached over I2C, bindings describe the
  uncontrolled mode.
- In this commit message, the same.
- In the commit message for the board DT mention your findings about the
  board, mention soldering R9 or R17 (which one?) and R27.
> 
> Dennis
> 
> > >
> > > > Signed-off-by: Dennis Gilmore <dennis at ausil.us>
> > > > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>
> > > > ---
> > > >  drivers/gpu/drm/bridge/simple-bridge.c | 5 +++++
> > > >  1 file changed, 5 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
> > > > index 8aa31ca3c72d..42c1f3d5ba0c 100644
> > > > --- a/drivers/gpu/drm/bridge/simple-bridge.c
> > > > +++ b/drivers/gpu/drm/bridge/simple-bridge.c
> > > > @@ -270,6 +270,11 @@ static const struct of_device_id simple_bridge_match[] = {
> > > >             .data = &(const struct simple_bridge_info) {
> > > >                     .connector_type = DRM_MODE_CONNECTOR_HDMIA,
> > > >             },
> > > > +   }, {
> > > > +           .compatible = "lontium,lt8711uxd",
> > > > +           .data = &(const struct simple_bridge_info) {
> > > > +                   .connector_type = DRM_MODE_CONNECTOR_HDMIA,
> > > > +           },
> > > >     }, {
> > > >             .compatible = "parade,ps185hdm",
> > > >             .data = &(const struct simple_bridge_info) {
> > >
> > > --
> > > Regards,
> > >
> > > Laurent Pinchart
> >
> > --
> > With best wishes
> > Dmitry

-- 
With best wishes
Dmitry