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

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Message-ID: <de4718f5-a36f-4e5c-b5e1-f1c6e2484420@baylibre.com>
Date: Fri, 6 Sep 2024 09:04:36 -0500
From: David Lechner <dlechner@...libre.com>
To: Nuno Sá <noname.nuno@...il.com>,
 Krzysztof Kozlowski <krzk@...nel.org>,
 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 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