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AJvYcCVqX99vjq3GhqbV0rgAo4ooEvlD4TBhMhr6lQ7HubryrLtsUq7botb3k1qHtNh6Fn448amK6osocK5NZyRb@vger.kernel.org, AJvYcCW0NWdrYJepEgd8CFrISxufAJxiw0deMDaBS+mpoFADADFP0wAUAtKDqBnJ/NILFe2yxtDeWND9G5hd@vger.kernel.org, AJvYcCXxn5F2f1iFsfq+i73j0nz/E2CYbr1GEi0EVZi8AgntJ77T3UHku8REsScSQjYgjk/WvtDeNNM7c2yn@vger.kernel.org X-Gm-Message-State: AOJu0YxjDVRak2Mgo3IYXklQCFUQNU1R6lk896vJAc2s6eBqhIWTGcvw 6wXLlueqJ5h53J29CtzqOaDYYocj7o5s4Z3ZLVeIIihekA+0Q5es X-Google-Smtp-Source: AGHT+IFl5HjqKgtqh+fb58lJhfu7d1Mkenyc6sw3dP4clRYllNpnSYITsEytxbyKR15bszKvq0csZg== X-Received: by 2002:a05:6000:4007:b0:378:7e94:d613 with SMTP id ffacd0b85a97d-37889682ae1mr1785635f8f.42.1725623603696; Fri, 06 Sep 2024 04:53:23 -0700 (PDT) Received: from nsa.fritz.box ([2001:a61:341e:1201:c434:b5b1:98a6:efed]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-374ba593876sm17883712f8f.5.2024.09.06.04.53.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Sep 2024 04:53:23 -0700 (PDT) Message-ID: <058937fa93d484f3e81807d08a39bd8dfd3358e8.camel@gmail.com> Subject: Re: [PATCH v2 5/9] dt-bindings: iio: dac: add ad3552r axi-dac compatible From: Nuno =?ISO-8859-1?Q?S=E1?= To: Krzysztof Kozlowski , Angelo Dureghello Cc: Lars-Peter Clausen , Michael Hennerich , Nuno =?ISO-8859-1?Q?S=E1?= , Jonathan Cameron , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Olivier Moysan , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, David Lechner Date: Fri, 06 Sep 2024 13:53:22 +0200 In-Reply-To: <1928d0ce-cad9-4737-880e-3759c47fddbc@kernel.org> References: <20240905-wip-bl-ad3552r-axi-v0-iio-testing-v2-0-87d669674c00@baylibre.com> <20240905-wip-bl-ad3552r-axi-v0-iio-testing-v2-5-87d669674c00@baylibre.com> <1928d0ce-cad9-4737-880e-3759c47fddbc@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.4 (3.52.4-1.fc40) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2024-09-06 at 11:37 +0200, Krzysztof Kozlowski wrote: > On 06/09/2024 11:11, Angelo Dureghello wrote: > > Hi Krzysztof, > >=20 > > 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 > > > >=20 > > > > Add a new compatible for the ad3552r variant of the generic DAC IP. > > > >=20 > > > > 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. > > > >=20 > > > > Signed-off-by: Angelo Dureghello > > > > --- > > > > =C2=A0 Documentation/devicetree/bindings/iio/dac/adi,axi-dac.yaml |= 1 + > > > > =C2=A0 1 file changed, 1 insertion(+) > > > >=20 > > > > 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: > > > > =C2=A0=C2=A0=C2=A0 compatible: > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 enum: > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - adi,axi-dac-9.1.b > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - 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? > > >=20 > > > And why versions are mixed with real products but without any > > > compatibility. What does the version express in such case? > >=20 > > dac-ad3552r IP (fpga) is a variant of the dac IP, very similar, > > about the version, it still reads as 9.1.b > >=20 > > so i can eventually change it to: > >=20 > > adi,axi-dac-ad3552-9.1.b > >=20 > > Should be more correct. >=20 > 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. >=20 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 anothe= r block (typical DMA as this is used for really high speed stuff) and the device. N= ow, 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 th= e base generic axi-adc). And in this design the IP is also acting as a qspi contro= ller for actually controlling the configuration of the device while, typically, IIO = backends are meant to only care about the dataplane. With all of this, there are dis= cussions still happening on the RFC (Angelo was too fast with this version) between = using different properties or new compatibles for changes so significant like thi= s on the generic IP. See the thread where Conor is also involved. > Third, versions are useless if you do not use them as fallbacks. >=20 In this particular case we can't use the generic IP as a fallback since wit= hout the bus controller feature the device can't really work. But it can happen we i= ncrease the version on the generic core and use the existing version as fallback= =20 > Something this is really broken and I don't know if the binding or this > patch. Having said the above, I'm really not sure if what we have is the best appr= oach but these are also early days (upstream) for this so we should still be able to= change things if we need too. I'm fairly sure there's still no one relying on this= so we should be able to change things in a breaking way (if we need to be that ex= treme). Thanks! - Nuno S=C3=A1