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

[spanda at codeaurora.org]

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