Re: [PATCH v5 2/4] dt-bindings: drm/bridge: Document sn65dsi86 bridge bindings

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On 2018-05-02 22:31, Stephen Boyd wrote:
Quoting Sandeep Panda (2018-05-01 21:32:00)
diff --git a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt
new file mode 100644
index 0000000..0d042ce
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi86.txt
@@ -0,0 +1,76 @@
+SN65DSI86 DSI to eDP bridge chip
+--------------------------------
+
+This is the binding for Texas Instruments SN65DSI86 bridge.
+http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=sn65dsi86&fileType=pdf
+
+Required properties:
+- compatible: Must be "ti,sn65dsi86"
+- reg: i2c address of the chip, 0x2d as per datasheet
+- enable-gpios: OF device-tree gpio specification for bridge_en pin
+
+- vccio-supply: A 1.8V supply that powers up the digital IOs.
+- vpll-supply: A 1.8V supply that powers up the displayport PLL.
+- vcca-supply: A 1.2V supply that powers up the analog circuits.
+- vcc-supply: A 1.2V supply that powers up the digital core.
+
+Optional properties:
+- interrupts: Specifier for the SN65DSI86 interrupt line.
+- hpd-gpios: OF device-tree gpio specifications for HPD pin.
+
+- refclk-freq-khz: Value specifying the frequency of reference clock in KHz unit.

Please use the clocks property instead. We may need to turn the clk on
first before this can work so the driver would use the clk framework (at
least in linux). clock-names could have 'refclk' because that's the pin
name.

Is there a way in DRM to figure out the frequency of the clock frequency
for DACP/N? It looks like if refclk is grounded, then the DACP/N pins
from the DSI side should be one of a set of frequencies, so I'm just
curious how that will work and if the binding would need to be updated
to indicate what the frequency of the DSI clock lane is, or if DRM can
tell this driver through the port/graph stuff somehow.


Can we do something like below?
1. Add a required dt-property to indicate what is the source of refclk, ti,sn-refclk-src = <0> ---> means refclk is derived from refclk pin. ti,sn-refclk-src = <1> ---> means refclk is derived from DACP/N pin. 2. Add a clock property to indicate the refclk frequency for refclk pin. 3. In driver, parse the refclk source dt-property. If the source is refclk pin then get the frquency from clock dt-property and program the i2c register accordingly. Else if the source is DACP/N pin then calculate the DSIA frequency based on current display mode (by the time we go for configuring refclk, drm_mode_set is already done and in diver we can calculate the frequency) and program the i2c register accordingly.

+
+- gpio-controller: Marks the device has a GPIO controller.
+- #gpio-cells: Number of GPIO cells. Refer to binding document "gpio/gpio.txt"

What's the number? 2?
number is 4, i will update this in binding

+- #pwm-cells : Number of cells used to specify a PWM. See pwm.txt in this directory
+              for a description of the cell formats.

What's the number? 1? There's a pwm.txt in this directory?
yes number is 1, i will update the binding. it should be pwm/pwm.txt
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