On Tue, 16 Jul 2024 at 12:24, Maxime Ripard <mripard@xxxxxxxxxx> wrote: > > Hi, > > On Mon, Jul 15, 2024 at 07:38:34PM GMT, Dmitry Baryshkov wrote: > > On Mon, 15 Jul 2024 at 17:42, Maxime Ripard <mripard@xxxxxxxxxx> 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. > > > > Please correct me if I'm wrong. We have following usecases. > > > > 1. I2C_EN pulled low. TI158 is in the pin strap mode, it is not > > connected to the I2C bus. A0, A1, SDA and SCL pins are used for > > strapping the settings. > > board DT file should describe the bridge as a platform device > > sitting directly under the root node. > > DT maintainers have required that reg is always present in the other > sub-thread. If I2C_EN is pulled low, there is no reg, as there is no i2c bus whatsoever. I2C pins are repurposed as pin straps, An pins are repurposed as pin straps. I think DT maintainers wanted reg for the 2.a. case - in other words the bridge is present on the I2C bus, but it is not being programmed. > > > 2. I2C_EN pulled high. TI158 is in the I2C mode. It is connected to > > the I2C bus, A0/A1 pins set the I2C bus address. The device is > > controlled over the I2C bus > > > > 2.a. The same as 2, but the device is not controlled at all, default > > settings are fine. > > > > The driver covers usecase 2.a. The bindings allow extending the driver > > to the usecase 2 (e.g. via optional properties which specify > > bord-specific settings) > > > > The usecase 1 is a completely separate topic, it requires a different > > schema file, specifying no i2c address, only voltages supplies and > > enable-gpios. > > I could have mis-unnderstood, but my understanding was that they were > running it with I2C_EN tied low. That was my initial assumption, but I think Arnoud pointed out that the bridge is connected to I2C, just not controlled as defaults are sane. > Of course, that's one of the thing that is completely missing from the > commit log, so who knows. Or from the cover letter :-( -- With best wishes Dmitry
