On Wed, Jul 24, 2024 at 07:28:41PM GMT, Marc Gonzalez wrote: > On 24/07/2024 19:25, Dmitry Baryshkov wrote: > > On Wed, Jul 24, 2024 at 07:18:39PM GMT, Marc Gonzalez wrote: > >> On 15/07/2024 16:42, Maxime Ripard wrote: > >>> On Mon, Jul 08, 2024 at 11:29:46PM GMT, Dmitry Baryshkov wrote: > >>>> On Mon, Jul 08, 2024 at 04:59:23PM GMT, Maxime Ripard wrote: > >>>>> On Mon, Jul 01, 2024 at 05:36:18PM GMT, Marc Gonzalez wrote: > >>>>>> On 01/07/2024 15:50, Maxime Ripard wrote: > >>>>>> > >>>>>>> On Thu, Jun 27, 2024 at 01:13:03PM GMT, Marc Gonzalez wrote: > >>>>>>> > >>>>>>>> TDP158 is an AC-coupled DVI / HDMI to TMDS level shifting Redriver. > >>>>>>>> It supports DVI 1.0, HDMI 1.4b and 2.0b. > >>>>>>>> It supports 4 TMDS channels, HPD, and a DDC interface. > >>>>>>>> It supports dual power supply rails (1.1V on VDD, 3.3V on VCC) > >>>>>>>> for power reduction. Several methods of power management are > >>>>>>>> implemented to reduce overall power consumption. > >>>>>>>> It supports fixed receiver EQ gain using I2C or pin strap to > >>>>>>>> compensate for different lengths input cable or board traces. > >>>>>>>> > >>>>>>>> Features > >>>>>>>> > >>>>>>>> - AC-coupled TMDS or DisplayPort dual-mode physical layer input > >>>>>>>> to HDMI 2.0b TMDS physical layer output supporting up to 6Gbps > >>>>>>>> data rate, compatible with HDMI 2.0b electrical parameters > >>>>>>>> - DisplayPort dual-mode standard version 1.1 > >>>>>>>> - Programmable fixed receiver equalizer up to 15.5dB > >>>>>>>> - Global or independent high speed lane control, pre-emphasis > >>>>>>>> and transmit swing, and slew rate control > >>>>>>>> - I2C or pin strap programmable > >>>>>>>> - Configurable as a DisplayPort redriver through I2C > >>>>>>>> - Full lane swap on main lanes > >>>>>>>> - Low power consumption (200 mW at 6Gbps, 8 mW in shutdown) > >>>>>>>> > >>>>>>>> https://www.ti.com/lit/ds/symlink/tdp158.pdf > >>>>>>>> > >>>>>>>> Signed-off-by: Marc Gonzalez <mgonzalez@xxxxxxxxxx> > >>>>>>>> --- > >>>>>>>> .../bindings/display/bridge/ti,tdp158.yaml | 51 ++++++++++++++++++++++ > >>>>>>>> 1 file changed, 51 insertions(+) > >>>>>>>> > >>>>>>>> diff --git a/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml > >>>>>>>> new file mode 100644 > >>>>>>>> index 0000000000000..21c8585c3bb2d > >>>>>>>> --- /dev/null > >>>>>>>> +++ b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml > >>>>>>>> @@ -0,0 +1,51 @@ > >>>>>>>> +# SPDX-License-Identifier: GPL-2.0-only > >>>>>>>> +%YAML 1.2 > >>>>>>>> +--- > >>>>>>>> +$id: http://devicetree.org/schemas/display/bridge/ti,tdp158.yaml# > >>>>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml# > >>>>>>>> + > >>>>>>>> +title: TI TDP158 HDMI to TMDS Redriver > >>>>>>>> + > >>>>>>>> +maintainers: > >>>>>>>> + - Arnaud Vrac <avrac@xxxxxxxxxx> > >>>>>>>> + - Pierre-Hugues Husson <phhusson@xxxxxxxxxx> > >>>>>>>> + > >>>>>>>> +properties: > >>>>>>>> + compatible: > >>>>>>>> + const: ti,tdp158 > >>>>>>>> + > >>>>>>>> + reg: > >>>>>>>> + description: I2C address of the device > >>>>>>>> + > >>>>>>>> + enable-gpios: > >>>>>>>> + description: GPIO controlling bridge enable > >>>>>>>> + > >>>>>>>> + vcc-supply: > >>>>>>>> + description: Power supply 3.3V > >>>>>>>> + > >>>>>>>> + vdd-supply: > >>>>>>>> + description: Power supply 1.1V > >>>>>>>> + > >>>>>>>> + ports: > >>>>>>>> + $ref: /schemas/graph.yaml#/properties/ports > >>>>>>>> + > >>>>>>>> + properties: > >>>>>>>> + port@0: > >>>>>>>> + $ref: /schemas/graph.yaml#/properties/port > >>>>>>>> + description: Bridge input > >>>>>>>> + > >>>>>>>> + port@1: > >>>>>>>> + $ref: /schemas/graph.yaml#/properties/port > >>>>>>>> + description: Bridge output > >>>>>>>> + > >>>>>>>> + required: > >>>>>>>> + - port@0 > >>>>>>>> + - port@1 > >>>>>>> > >>>>>>> The device supports DVI, HDMI or DP input, with various requirements and > >>>>>>> capabilities depending on the input. Your binding doesn't address that. > >>>>>>> > >>>>>>> Similarly, it can do lane-swapping, so we should probably have a > >>>>>>> property to describe what mapping we want to use. > >>>>>>> > >>>>>>> The i2c register access (and the whole behaviour of the device) is > >>>>>>> constrained on the I2C_EN pin status, and you can't read it from the > >>>>>>> device, so it's also something we need to have in the DT. > >>>>>> > >>>>>> We are using the device in its default configuration. > >>>>>> (Power on via OE, then it works as expected) > >>>>> > >>>>> I know, but that doesn't really matter for a binding. > >>>>> > >>>>>> Can we leave any additional properties to be defined by whomever needs > >>>>>> them in the future? > >>>>> > >>>>> If you can guarantee that doing so would be backward compatible, sure. > >>>>> But that means being able to answer those questions with a reasonable > >>>>> plan. > >>>> > >>>> I think proposed bindings are generic enough to cover other possible > >>>> usecases in future. > >>> > >>> I don't think it is. The current binding is for a I2C device that > >>> shouldn't be accessed through I2C. > >>> > >>> It's working for now because the driver doesn't do any access, so it's > >>> all great, but as soon as we add support for the other case, then we'll > >>> have to add a property that states that while it's an i2c device, it > >>> shouldn't be accessed. > >>> > >>> And adding such a property is a compatibility-breaking change. > >> > >> Why do you say: > >> "current binding is for a I2C device that > >> shouldn't be accessed through I2C" ? > >> > >> As a matter of fact, my debug code queries the device ID using > >> regmap_read() to make sure I set the correct I2C address. > > > > Please note: bingdings do not cover the driver at all. The driver might > > do whatever it wants. The bindings describe the hardware. > > OK. > How does the proposed binding say > "I2C device shouldn't be accessed through I2C" ? It doesn't, but then again, neither your commit log or cover letter say "it can be accessed by i2c" either, so we went on the wrong track. Maxime
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