Re: [PATCH v5 1/2] dt-bindings: usb: add analogix,anx7688.yaml

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Hi,

On 05.03.21 16:19, Laurent Pinchart wrote:
Hi Dafna,

On Fri, Mar 05, 2021 at 04:14:03PM +0100, Dafna Hirschfeld wrote:
On 05.03.21 15:34, Laurent Pinchart wrote:
On Fri, Mar 05, 2021 at 01:43:50PM +0100, Dafna Hirschfeld wrote:
ANX7688 is a USB Type-C port controller with a MUX. It converts HDMI 2.0 to
DisplayPort 1.3 Ultra-HDi (4096x2160p60).
The integrated crosspoint switch (the MUX) supports USB 3.1 data transfer
along with the DisplayPort Alternate Mode signaling over USB Type-C.
Additionally, an on-chip microcontroller (OCM) is available to manage the
signal switching, Channel Configuration (CC) detection, USB Power
Delivery (USB-PD), Vendor Defined Message (VDM) protocol support and other
functions as defined in the USB TypeC and USB Power Delivery
specifications.

ANX7688 is found on Acer Chromebook R13 (elm) and on
Pine64 PinePhone.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>
---
   .../bindings/usb/analogix,anx7688.yaml        | 177 ++++++++++++++++++
   1 file changed, 177 insertions(+)
   create mode 100644 Documentation/devicetree/bindings/usb/analogix,anx7688.yaml

diff --git a/Documentation/devicetree/bindings/usb/analogix,anx7688.yaml b/Documentation/devicetree/bindings/usb/analogix,anx7688.yaml
new file mode 100644
index 000000000000..6c4dd6b4b28b
--- /dev/null
+++ b/Documentation/devicetree/bindings/usb/analogix,anx7688.yaml
@@ -0,0 +1,177 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/usb/analogix,anx7688.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analogix ANX7688 Type-C Port Controller with HDMI to DP conversion
+
+maintainers:
+  - Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
+  - Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
+
+description: |
+  ANX7688 is a USB Type-C port controller with a MUX. It converts HDMI 2.0 to
+  DisplayPort 1.3 Ultra-HDi (4096x2160p60).
+  The integrated crosspoint switch (the MUX) supports USB 3.1 data transfer along with
+  the DisplayPort Alternate Mode signaling over USB Type-C. Additionally,
+  an on-chip microcontroller (OCM) is available to manage the signal switching,
+  Channel Configuration (CC) detection, USB Power Delivery (USB-PD), Vendor
+  Defined Message (VDM) protocol support and other functions as defined in the
+  USB TypeC and USB Power Delivery specifications.
+
+

Extra blank line ?

+properties:
+  compatible:
+    const: analogix,anx7688
+
+  reg:
+    maxItems: 1
+
+  avdd33-supply:
+    description: 3.3V Analog core supply voltage.
+
+  dvdd18-supply:
+    description: 1.8V Digital I/O supply voltage.
+
+  avdd18-supply:
+    description: 1.8V Analog core power supply voltage.
+
+  avdd10-supply:
+    description: 1.0V Analog core power supply voltage.
+
+  dvdd10-supply:
+    description: 1.0V Digital core supply voltage.
+

That's lots of supplies. If there's a reasonable chance that some of
them will always be driven by the same regulator (especially if the
ANX7688 documentation requires that), then they could be grouped. For
instance dvdd18-supply and avdd18-supply could be grouped into
vdd18-supply. It would still allow us to extend the bindings in a
backward compatible way later if a system uses different regulators. You
have more information about the hardware than I do, so it's your call.

Can you explain what do you mean by 'grouped' ?
Do you mean that instead of having two properties dvdd18-supply and avdd18-supply
I have only one property vdd18-supply?


+  hdmi5v-supply:
+    description: 5V power supply for the HDMI.
+
+  hdmi_vt-supply:
+    description: Termination voltage for HDMI input.

Maybe hdmi-vt-supply ?

+
+  clocks:
+    description: The input clock specifier.
+    maxItems: 1

How about

      items:
        - description: The input clock specifier.

+
+  clock-names:
+    items:
+      - const: xtal
+
+  hpd-gpios:
+    description: |
+      In USB Type-C applications, DP_HPD has no use. In standard DisplayPort
+      applications, DP_HPD is used as DP hot-plug.
+    maxItems: 1
+
+  enable-gpios:
+    description: Chip power down control. No internal pull-down or pull-up resistor.
+    maxItems: 1
+
+  reset-gpios:
+    description: Reset input signal. Active low.
+    maxItems: 1
+
+  vbus-det-gpios:
+    description: |
+      An input gpio for VBUS detection and high voltage detection,
+      external resistance divide VBUS voltage to 1/8.
+    maxItems: 1
+
+  interrupts:
+    description: |
+      The interrupt notifies 4 possible events - TCPC ALERT int, PD int, DP int, HDMI int.
+    maxItems: 1
+
+  cabledet-gpios:
+    description: An output gpio, indicates by the device that a cable is plugged.
+    maxItems: 1
+
+  vbus-ctrl-gpios:
+    description:
+      External VBUS power path. Enable VBUS source and disable VBUS sink or vice versa.
+    maxItems: 1
+
+  vconn-en1-gpios:
+    description: Controls the VCONN switch on the CC1 pin.
+    maxItems: 1
+
+  vconn-en2-gpios:
+    description: Controls the VCONN switch on the CC2 pin.
+    maxItems: 1
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for HDMI input.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: USB port for the USB3 input.
+
+      port@2:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: USB Type-c connector, see connector/usb-connector.yaml.
+
+    required:
+      - port@0

As all the ports exist at the hardware level, should they always be
present ? The endpoints are optional of course, in case a port isn't
connected on a particular system.

+
+required:
+  - compatible
+  - reg

Shouldn't clocks and regulators be also required ?

hmm, theoretically yes. Practically, in the case of Acer R13 (mediatek elm) device,
the ANX7688 is powered up and controlled by the Embedded Controller. The kernel only
needs to read few registers from that device for the drm bridge driver.
(also mentioned that in the cover letter).

This may not be a popular opinion, but if the ANX7688 is fully
controlled by the EC, I wonder if we shouldn't have an "EC DRM bridge"
driver that would interrogate the EC instead :-)

But the driver in patch 2/2 do access the anx7688 device with I2C.
It does interrogate the EC.


Is there a risk of bus conflicts if the EC and the main SoC try to
access the ANX7688 over I2C at the same time ?

The SoC access the anx7688 though something called 'i2c-tunnel' (see google,cros-ec-i2c-tunnel.yaml)
So the I2C tunnels though the EC (I don't know how this is really implemented to be honest).


Thanks,
Dafna


Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>

+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c0 {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        anx7688: anx7688@2c {
+            compatible = "analogix,anx7688";
+            reg = <0x2c>;
+            avdd33-supply = <&reg_dcdc1>;
+            dvdd18-supply = <&reg_ldo_io1>;
+            avdd18-supply = <&reg_ldo_io1>;
+            avdd10-supply = <&reg_anx1v0>;
+            dvdd10-supply = <&reg_anx1v0>;
+            hdmi_vt-supply = <&reg_dldo1>;
+            enable-gpios = <&pio 3 10 GPIO_ACTIVE_LOW>; /* PD10 */
+            reset-gpios = <&pio 3 6 GPIO_ACTIVE_HIGH>; /* PD6 */
+            interrupt-parent = <&r_pio>;
+            interrupts = <0 11 IRQ_TYPE_EDGE_FALLING>; /* PL11 */
+            cabledet-gpios = <&r_pio 0 8 GPIO_ACTIVE_HIGH>; /* PL8 */
+            vconn-en1-gpios = <&pio 3 9 GPIO_ACTIVE_LOW>; /* PD9 */
+            vconn-en2-gpios = <&pio 3 9 GPIO_ACTIVE_LOW>; /* PD9 */
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                port@0 {
+                    reg = <0>;
+                    anx7688_in0: endpoint {
+                        remote-endpoint = <&hdmi0_out>;
+                    };
+                };
+
+                port@1 {
+                    reg = <1>;
+                    anx7688_in1: endpoint {
+                        remote-endpoint = <&usbdrd_phy_ss>;
+                    };
+                };
+                port@2 {
+                    reg = <2>;
+                    anx7688_out: endpoint {
+                        remote-endpoint = <&typec_connector>;
+                    };
+                };
+            };
+        };
+    };

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