linux-kernel - Re: [PATCH v2 5/9] dt-bindings: iio: dac: add ad3552r axi-dac compatible

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Message-ID: <9894666e-30bf-42c0-88a0-18ce2a9300a2@baylibre.com>
Date: Fri, 6 Sep 2024 11:42:13 -0500
From: David Lechner <dlechner@...libre.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Nuno Sá
 <noname.nuno@...il.com>, Angelo Dureghello <adureghello@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Olivier Moysan <olivier.moysan@...s.st.com>,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/9] dt-bindings: iio: dac: add ad3552r axi-dac
 compatible

On 9/6/24 11:36 AM, Krzysztof Kozlowski wrote:
> On 06/09/2024 16:04, David Lechner wrote:
>> On 9/6/24 8:52 AM, Nuno Sá wrote:
>>> On Fri, 2024-09-06 at 14:13 +0200, Krzysztof Kozlowski wrote:
>>>> On 06/09/2024 13:53, Nuno Sá wrote:
>>>>> On Fri, 2024-09-06 at 11:37 +0200, Krzysztof Kozlowski wrote:
>>>>>> On 06/09/2024 11:11, Angelo Dureghello wrote:
>>>>>>> Hi Krzysztof,
>>>>>>>
>>>>>>> On 06/09/24 9:22 AM, Krzysztof Kozlowski wrote:
>>>>>>>> On Thu, Sep 05, 2024 at 05:17:35PM +0200, Angelo Dureghello wrote:
>>>>>>>>> From: Angelo Dureghello <adureghello@...libre.com>
>>>>>>>>>
>>>>>>>>> Add a new compatible for the ad3552r variant of the generic DAC IP.
>>>>>>>>>
>>>>>>>>> The ad3552r DAC IP variant is very similar to the generic DAC IP,
>>>>>>>>> register map is the same, but some register fields are specific to
>>>>>>>>> this IP, and also, a DDR QSPI bus has been included in the IP.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
>>>>>>>>> ---
>>>>>>>>>   Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml | 1 +
>>>>>>>>>   1 file changed, 1 insertion(+)
>>>>>>>>>
>>>>>>>>> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
>>>>>>>>> b/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
>>>>>>>>> index a55e9bfc66d7..c0cccb7a99a4 100644
>>>>>>>>> --- a/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
>>>>>>>>> +++ b/Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml
>>>>>>>>> @@ -24,6 +24,7 @@ properties:
>>>>>>>>>     compatible:
>>>>>>>>>       enum:
>>>>>>>>>         - adi,axi-dac-9.1.b
>>>>>>>>> +      - adi,axi-dac-ad3552r
>>>>>>>> I am sorry, but what is the product here? It looks like either wrong
>>>>>>>> order or even completely redundant. What is ad3552r?
>>>>>>>>
>>>>>>>> And why versions are mixed with real products but without any
>>>>>>>> compatibility. What does the version express in such case?
>>>>>>>
>>>>>>> dac-ad3552r IP (fpga) is a variant of the dac IP, very similar,
>>>>>>> about the version, it still reads as 9.1.b
>>>>>>>
>>>>>>> so i can eventually change it to:
>>>>>>>
>>>>>>> adi,axi-dac-ad3552-9.1.b
>>>>>>>
>>>>>>> Should be more correct.
>>>>>>
>>>>>> No. First ad3552r is the product, so axi-dac is redundant. Second why
>>>>>> adding versions if you have product names? Versioning was allowed
>>>>>> because apparently that's how these are called, but now it turns out it
>>>>>> is not version but names.
>>>>>>
>>>>>
>>>>> Let me try to explain on how this whole thing works...
>>>>>
>>>>> We have a generic FPGA IP called axi-dac (same story is true for the other axi-
>>>>> adc
>>>>> IP) which adds some basic and generic capabilities like DDS (Direct digital
>>>>> synthesis) and the generic one is the compatible existing now. This IP is a so
>>>>> called
>>>>> IIO backend because it then connects to a real converter (in this case DACs)
>>>>> extending it's capabilities and also serving as an interface between another
>>>>> block
>>>>> (typical DMA as this is used for really high speed stuff) and the device. Now,
>>>>> depending on the actual device, we may need to add/modify some features of the IP
>>>>> and
>>>>> this is what's happening for the ad3552r DAC (it's still build on top of the 
>>>>
>>>> What is "ad3552"? DAC right? Then as I said axi-dac is redundant. We do
>>>> not call ti,tmp451 a ti,sensor-tmp451, right?
>>>>
>>>
>>> Yes, I agree the DAC part is redundant. But I think the axi prefix (or suffix) is
>>> meaningful to differentiate it from the bindings for the device itself.
>>>
>> The binding is for this [1] IP core. The documentation calls the core
>> "AXI AD3552R", so I agree that "adi,axi-ad2552r" is the most sensible
>> compatible name.
>>
>> http://analogdevicesinc.github.io/hdl/library/axi_ad3552r/index.html
> 
> I don't see any AXI here:
> https://www.analog.com/en/products/ad3552r.html
> Neither here:
> https://www.analog.com/media/en/technical-documentation/data-sheets/ad3552r.pdf
> 
> Are these different?


Yes, they are different. AD2553R is the DAC chip itself. But "AXI AD2553R" is an
FPGA IP block designed specifically for use with that chip.