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

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Message-ID: <bb25003f-3a30-4d73-9b40-447d2d513fb3@kernel.org>
Date: Fri, 6 Sep 2024 18:36:18 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: David Lechner <dlechner@...libre.com>, 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 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?

Best regards,
Krzysztof