From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D5D811187; Wed, 2 Oct 2024 05:54:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727848470; cv=none; b=LoifU7VA+t4SKVpe2z57X0KYysHXL/Uq8hm+7eQb3jjysZfH+1fUndYF5iRgHt51TSAREMIhC8QRIDuKXXmP86uYSPqyWChPqq/9jw1vDLdPCLEtmXMOSl+mScsUjeFxijqwTXQLgNdJs3x0K6AcTDDYUIczfUnf5quFg7mjsh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727848470; c=relaxed/simple; bh=YAqpkl2qdYR4cLzqr7b2lKzHkUIZFe56wgjmq+h+kow=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=OA7++z4yVFpzY+VNgiYrsYIySgqpd1iSDjgCQ6SEETMJyCWXiC83c6i1Pf4nU7qrz5bx3nUxuhYzIDiNW4Z2kqx067Ett7OmpoUA+PDNb7V9APR2yabx7ypfllByP2Jqu8wP3GfrqP75OsBKq7TJIhJgNpLWOqyuiN0xgmt9UEs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qF2EIlZt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qF2EIlZt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 664C3C4CEC5; Wed, 2 Oct 2024 05:54:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727848470; bh=YAqpkl2qdYR4cLzqr7b2lKzHkUIZFe56wgjmq+h+kow=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=qF2EIlZtAjZ90sFHR0LY4S0bZu7ak0smm3LWlCNcyXywxwC/JPjoglskSj6QhWEAi WpoiX/EIoMuF57mUq11mGlXCETVTpIvy0bMfdOgTR79FPCAQQdCW9VcCcFHY4xmYGs CeyYy3nqKu2TiXLQCcHAKE7qjdoYfJwgOisyjzJOhiNTXM2IL1/qIcEVxPTlry62Td J5JAo7MabVlKOUqLxTuZFHZZXGoWNQ1dcqcl/QsxESPkuWF2TZ63yppDzCq7m3W+jF RQ5wIJpUyu/T6hRWOIZG37JFcnhqaXyFb1s+0g+hAgx84ne39uQFNrfAsdyyXMyfmg jLZAqVKf9G4Ow== Message-ID: Date: Wed, 2 Oct 2024 07:54:22 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 04/10] dt-bindings: iio: dac: ad3552r: add io-backend support To: Jonathan Cameron , =?UTF-8?Q?Nuno_S=C3=A1?= Cc: Jonathan Cameron , Angelo Dureghello , Lars-Peter Clausen , Michael Hennerich , Nuno Sa , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Olivier Moysan , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, dlechner@baylibre.com References: <20240919-wip-bl-ad3552r-axi-v0-iio-testing-v3-4-a17b9b3d05d9@baylibre.com> <418a8a9b-3bcf-4b8f-92a0-619a3bf26ab5@baylibre.com> <0279203b6cd9f1312d9c03654c262c04ac12fbd9.camel@gmail.com> <28834db1-3e9e-47f4-b00e-a548589d77e9@kernel.org> <20240929115919.0318034c@jic23-huawei> <20240930160947.00007c8a@Huawei.com> <80eb0949508d31a55f2b8ab999210a7c7cd5cbe2.camel@gmail.com> <20241001192913.5b848dfc@jic23-huawei> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 01/10/2024 20:29, Jonathan Cameron wrote: >>> >>> Makes all sorts of assumptions about the SPI controllers being designed >>> for multi controllers on the same SPI buses but I'm not aware of a reason >>> you can't do that. >>> >>> As the only control message that would need to go over the offload engine >>> would be the exit DDR (I think) that might be hard coded into a slightly >>> simpler soft IP along with the bulk data transfer stuff. >>> >> >> Not even sure if DDR would be a problem. Right now, I __think__ we need to >> enable DDR both the peripheral and on the backend. On the peripheral we could >> use the control link on the non offload controller. On the offload controller, >> we would set it through IIO backend and that would be a backend config and not >> go over the bus. > > It's the path back to SDR that I wasn't sure about as it might need a > DDR register write? > >> >> To make a correction on my previous reply to Krzysztof, the HW folks made some >> experiments with the SPI ENIGINE IP (with the offload engine) but without the >> AXI DAC IP. So, effectively only one controller in place. That said, I'm also >> not seeing any reason why something like the above would not be possible. > > Conclusion / summary for Krzystoff and other DT binding > folk. It's possible to use this with another backend (which no one has > written the IP for yet) so I (at least) think the reference is needed > even though the only one we have right now is also the parent. > > Driver wise, we could in theory poke the parent if the property isn't there > on the off chance it is a suitable backend, but we can't assume that's > the one in use even if it has some suitable support. Maybe there > is a more capable one double wired? > > So I'd like to keep the io-backend phandle there. Ack. Best regards, Krzysztof