linux-kernel - Re: [PATCH 1/4] dt-bindings: media: Binding document for Qualcomm Camera Control Interface driver

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Date:   Thu, 12 Oct 2017 17:50:03 +0300
From:   Todor Tomov <todor.tomov@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     wsa@...-dreams.de, linux-i2c@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/4] dt-bindings: media: Binding document for Qualcomm
 Camera Control Interface driver

Hi Bjorn,

Thank you for the review.

On  6.10.2017 08:29, Bjorn Andersson wrote:
> On Mon 02 Oct 07:13 PDT 2017, Todor Tomov wrote:
>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-qcom-cci.txt b/Documentation/devicetree/bindings/i2c/i2c-qcom-cci.txt
>> new file mode 100644
>> index 0000000..f4c5338
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/i2c/i2c-qcom-cci.txt
>> @@ -0,0 +1,55 @@
>> +Qualcomm Camera Control Interface I2C controller
> 
> Well, it's not a I2C controller, it is a MIPI CCI controller.
> 
>> +
>> +Required properties:
>> + - compatible: Should be one of:
>> +   - "qcom,cci-v1.0.8" for 8916;
>> +   - "qcom,cci-v1.4.0" for 8996.
>> + - #address-cells: Should be <1>.
>> + - #size-cells: Should be <0>.
>> + - reg: Base address of the controller and length of memory mapped region.
>> + - reg-names: Should be "cci".
> 
> No need for reg-names, as we only have one.
> 
>> + - interrupts: Specifier for CCI interrupt.
>> + - interrupt-names: Should be "cci".
> 
> No need for interrupt-names, as we only have one.
> 
>> + - clocks: List of clock specifiers, one for each entry in clock-names.
>> + - clock-names: Should contain:
>> +   - "mmss_mmagic_ahb" - on 8996 only;
>> +   - "camss_top_ahb";
>> +   - "cci_ahb";
>> +   - "cci";
>> +   - "camss_ahb".
>> + - pinctrl-names: Should contain only one value - "default".
>> + - pinctrl-0: Pin control group to be used for this controller.
> 
> No need to document that the node can have the default pinctrl
> properties.
> 
>> +
>> +
>> +Required properties on 8996:
>> + - power-domains: Power domain specifier.
>> +
>> +Optional:
>> + - clock-frequency: Desired I2C bus clock frequency in Hz, defaults to 100 kHz
>> +   if omitted.
>> +
>> +Example:
>> +
>> +                cci: qcom,cci@...000 {
> 
> Don't do qcom, in the node name, and there's probably no reason to have
> a label for this node either. So just make it
> 
> 		   cci@...000 {
> 
>> +                        compatible = "qcom,cci-v1.4.0";
>> +                        #address-cells = <1>;
>> +                        #size-cells = <0>;
>> +                        reg = <0xa0c000 0x1000>;
>> +                        reg-names = "cci";
>> +                        interrupts = <GIC_SPI 295 IRQ_TYPE_EDGE_RISING>;
>> +                        interrupt-names = "cci";
>> +                        power-domains = <&mmcc CAMSS_GDSC>;
>> +                        clocks = <&mmcc MMSS_MMAGIC_AHB_CLK>,
>> +                                        <&mmcc CAMSS_TOP_AHB_CLK>,
>> +                                        <&mmcc CAMSS_CCI_AHB_CLK>,
>> +                                        <&mmcc CAMSS_CCI_CLK>,
>> +                                        <&mmcc CAMSS_AHB_CLK>;
>> +                        clock-names = "mmss_mmagic_ahb",
>> +                                        "camss_top_ahb",
>> +                                        "cci_ahb",
>> +                                        "cci",
>> +                                        "camss_ahb";
>> +                        pinctrl-names = "default";
>> +                        pinctrl-0 = <&cci0_default>;
>> +                        clock-frequency = <400000>;
>> +                };
> 
> In the case of this single cci block having two masters we need a way to
> describe the two sets of clients. I think the two options we have are:
> 
> cci {
> 	client {
> 		reg = <0 0x2c>;
> 	};
> };
> 
> The reg here being <master address>
> 
> or:
> 
> cci {
> 	master0 {
> 		client {
> 			reg = <0x2c>;
> 		};
> 	};
> };
> 
> The name "master0" could be made significant and picked up by name, and
> in the case of single-master this level could be omitted.
> 
> 
> I like the first one, but it looks really hard to get implemented in
> Linux, based on the i2c core's expectation that #address-cells is 1. So
> I think the latter is the favourable option.

Yes, I'll try this for the version which supports the second bus. Thank
you for this suggestion.

The rest of the points I'll fix now and send a v2.

> 
> Regards,
> Bjorn
> 

-- 
Best regards,
Todor Tomov