From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay2-d.mail.gandi.net (relay2-d.mail.gandi.net [217.70.183.194]) (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 930683612E; Mon, 19 Feb 2024 13:41:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.194 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708350090; cv=none; b=pxz4X8VsQIngGHB7WlAf2p28WRt8vnQ6HVGEarqgGaeoQQ3CnkQRfhK8XhZdCJa9evcRjtEGAJ9tkSDfK+OhTKUbsOjtGaelAEQhHLTQmi+/xNKICnEwuwjd0QNClPEO4C88rCXVYRvWIMIBeiRG9qlArMEZTWJSj66WqLwz60Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708350090; c=relaxed/simple; bh=fGpvwIGy2LQRXThEEta3A8xVTtWdS4NNyyyJxz4ZWoE=; h=Mime-Version:Content-Type:Date:Message-Id:Cc:To:From:Subject: References:In-Reply-To; b=fZXVuQE6HelgQvZEoQj7x94ucU5+XcVMNR7lHM9D6W4ksirGhRL+UV4JSLTxA2DTIYbkRncOBu3nNJN+gespSYkQOLYjdHapRzVxu8sdv97bWs68OzuvrFARxivpyZkPWkJyb+/ptnBBLHBUKNYLVE2nQ9lCI0FZtEvb2h85MC4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com; spf=pass smtp.mailfrom=bootlin.com; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b=KKX55vGX; arc=none smtp.client-ip=217.70.183.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=bootlin.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bootlin.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com header.b="KKX55vGX" Received: by mail.gandi.net (Postfix) with ESMTPSA id 6892B40007; Mon, 19 Feb 2024 13:41:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1708350085; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=npYRmHh0n3z51AZdDa3QZzAz5BYIy4ErQyiNWsy/7k8=; b=KKX55vGXkgAsul0jJVBBh0WsHdH8Ty2o0BPwgXrX+pRSA/sZsj+tCny78oV9IMd9+Ypv8W yZOLwdTULOXg6jjFRTUj6/M/B46V7Ub/8tc7aJHs2pPxMCGhUPYGUfPiDcVpgvsDkzMpgi 5xBswwSooElotlLj4fWUbsWevhqaY58Mws6Tur2cwC3A0wDMfqWg/b01Xpxrd1aLDQATo0 LJPXMx8Qw45HmDL1SUVlB8rPrDo5GRkU6oMayDC5RkmgYarbfNpaZ4logH21A3pmOChH6W VyspoZjQqPJoVXA35x/79EEd5M/Ik5ProNlLxlZ21A5P6WVZVJKqaOp3tn1O0g== Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 19 Feb 2024 14:41:24 +0100 Message-Id: Cc: "Linus Walleij" , "Andi Shyti" , "Krzysztof Kozlowski" , "Conor Dooley" , "Thomas Bogendoerfer" , , , , , , "Gregory Clement" , "Vladimir Kondratiev" , "Thomas Petazzoni" , "Tawfik Bayouk" To: "Krzysztof Kozlowski" , "Rob Herring" From: =?utf-8?q?Th=C3=A9o_Lebrun?= Subject: Re: [PATCH 02/13] dt-bindings: i2c: nomadik: add mobileye,eyeq5-i2c bindings and example X-Mailer: aerc 0.15.2 References: <20240215-mbly-i2c-v1-0-19a336e91dca@bootlin.com> <20240215-mbly-i2c-v1-2-19a336e91dca@bootlin.com> <20240216022227.GA850600-robh@kernel.org> <6effca50-29a4-43b9-86eb-310bd4e08e5c@linaro.org> In-Reply-To: X-GND-Sasl: theo.lebrun@bootlin.com Hello, On Sat Feb 17, 2024 at 9:25 AM CET, Krzysztof Kozlowski wrote: > On 16/02/2024 11:40, Th=C3=A9o Lebrun wrote: > > On Fri Feb 16, 2024 at 11:33 AM CET, Krzysztof Kozlowski wrote: > >> On 16/02/2024 11:18, Th=C3=A9o Lebrun wrote: > >>> > >>>>> + mobileye,id: > >>>>> + $ref: /schemas/types.yaml#/definitions/uint32 > >>>>> + description: Platform-wide controller ID (integer starti= ng from zero). > >>>> > >>>> instance indexes are a NAK. You can use i2cN aliases if you must. > >>>> > >>>> Why do you need it? To access OLB? If so, add cell args to the OLB= =20 > >>>> phandle instead. > >>> > >>> Why we do what we do: I2C controller must write a 2 bit value dependi= ng > >>> on the bus speed. All I2C controllers write into the same register. > >> > >> Which register? Your devices do not share IO address space. > >=20 > > mobileye,olb is a prop with a phandle to a syscon. That syscon contains > > the register we are interested in. > > So exactly what Rob said... I don't understand why you have chosen to go > with alias. I had misunderstood Rob's original message. Now that I've done some tests to use cells I get what was meant. I'd have a follow-up question. What should the cells contain? I see two options: - phandle + I2C controller global index (from 0 thru 4). Then Linux (or other) driver know how to map that index to register + mask combo. ie: i2c2: i2c@500000 { compatible =3D "mobileye,eyeq5-i2c", "arm,primecell"; reg =3D <0 0x500000 0x0 0x1000>; /* ... */ mobileye,olb =3D <&olb 2>; }; - phandle + register offset + mask. ie: i2c2: i2c@500000 { compatible =3D "mobileye,eyeq5-i2c", "arm,primecell"; reg =3D <0 0x500000 0x0 0x1000>; /* ... */ mobileye,olb =3D <&olb 0xB8 0x300>; /* phandle + offset + mask */ }; I would have guessed the second approach was frown upon as DT aren't meant to contain iomem offsets. However I'm seeing quite a few drivers using this approach, and no driver doing the first approach. Maybe my instinct isn't leading me the right way. See those bindings that use the second approach. They were found because their drivers use the syscon_regmap_lookup_by_phandle_args() function call. I've added the file creation date to highlight recent bindings (that hopefully are closer to the right way). - phy/starfive,jh7110-pcie-phy.yaml 2023-06-29T15:51:12+08:00 - usb/starfive,jh7110-usb.yaml 2023-05-18T19:27:48+08:00 - net/starfive,jh7110-dwmac.yaml 2023-04-17T18:02:49+08:00 - phy/qcom,sc8280xp-qmp-pcie-phy.yaml 2022-11-05T15:59:34+01:00 - sound/snps,designware-i2s.yaml 2022-07-01T20:22:49+01:00 - pinctrl/canaan,k210-fpioa.yaml 2020-12-13T22:50:44+09:00 - media/ti,cal.yaml 2019-11-12T15:53:47+01:00 I know looking at existing drivers/bindings isn't the right way, but I have no other frame of reference. That's why I'm asking for guidance on this one. Thanks, -- Th=C3=A9o Lebrun, Bootlin Embedded Linux and Kernel engineering https://bootlin.com ------------------------------------------------------------------------