Re: [PATCH RFC 4/7] i2c: Add device tree bindings for GENI I2C Controller

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On Mon, Jan 8, 2018 at 6:33 PM, Karthik Ramasubramanian
<kramasub@xxxxxxxxxxxxxx> wrote:
>
>
> On 1/2/2018 8:51 AM, Rob Herring wrote:
>>
>> On Wed, Dec 27, 2017 at 09:27:23AM -0700, Karthikeyan Ramasubramanian
>> wrote:
>>>
>>> Add device tree binding support for I2C Controller in GENI based
>>> QUP Wrapper.
>>>
>>> Signed-off-by: Sagar Dharia <sdharia@xxxxxxxxxxxxxx>
>>> Signed-off-by: Karthikeyan Ramasubramanian <kramasub@xxxxxxxxxxxxxx>
>>> ---
>>>   .../devicetree/bindings/i2c/i2c-qcom-geni.txt      | 39
>>> ++++++++++++++++++++++
>>>   1 file changed, 39 insertions(+)
>>>   create mode 100644
>>> Documentation/devicetree/bindings/i2c/i2c-qcom-geni.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-qcom-geni.txt
>>> b/Documentation/devicetree/bindings/i2c/i2c-qcom-geni.txt
>>> new file mode 100644
>>> index 0000000..d2fa9ce
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/i2c/i2c-qcom-geni.txt
>>> @@ -0,0 +1,39 @@
>>> +Qualcomm Technologies Inc. GENI based I2C Controller driver
>>> +
>>> +Required properties:
>>> + - compatible: Should be:
>>> +   * "qcom,i2c-geni.
>>
>>
>> Only 1 version?
>
> The Serial Engine used by I2C protocol has the same version as the QUP h/w
> version. The QUP Wrapper driver exposes an interface function to get the h/w
> version so that I2C controller driver can support version-specific
> operations, if any.
>>
>>
>>> + - reg: Should contain QUP register address and length.
>>> + - interrupts: Should contain I2C interrupt.
>>> + - clocks: Serial engine core clock, and AHB clocks needed by the
>>> device.
>>
>>
>> Are there really clocks for a firmware based device or these are just
>> clocks in the parent serial engine?
>
> The clocks are required to derive the protocol clock. The clocks are also
> required by the Serial Engine to access the System Memory during DMA mode of
> operation.

You can get the QUP core (or Serial engine?) node and then get its
clocks if you need to know the frequency. Put the clocks in DT in the
h/w block they belong to. If you don't really have an I2C clock in the
h/w, don't put one in the DT.

Rob
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