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 167FA2AEE3; Thu, 18 Jul 2024 15:59:54 +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=1721318395; cv=none; b=LEHKAyZt2o8QXZZccqkm4T3f4QjSG0C7n88EcI++sA1NwYmCb+K66f+I+ZtyMflXGLsGmy/XlAuPLIhTOStIw6gQUO1wJV2RJRIf6M23S9pgiuxUftc1466zCbtj3NVF65E5oy1QyRLhs8YEnwOddwglACXQsIeTjv5X05rYNtQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721318395; c=relaxed/simple; bh=T4DfjvkHoIEyUPZXgAngg+UvPIuZJXu0JXGh6sWNt+c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PFuGf+jQJyBMuhzl9f9r6JuNlWMI8/ollRxCYg/J9dE+FmbMA+znpVxm/9U+Ok/r+OABb4g0844Xwt9uuDO4tjH41g/zpBoFZLnw+F9CX6ewG66Dj0wbwvnUsL3D+yI6VrKcD3jBaeOE6VnA/0JWdrQlNEUlTIsSa+ntyHsjmMo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H5vHfytm; 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="H5vHfytm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74CC4C116B1; Thu, 18 Jul 2024 15:59:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721318394; bh=T4DfjvkHoIEyUPZXgAngg+UvPIuZJXu0JXGh6sWNt+c=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=H5vHfytmqPrYO2pIj4jHkuG37Chv40x0l0h3Sl9muo3W743GzaXi685mZhYM0PxKX qY1W1G26W7T74h+GzelvwecVAFTeTXk9rS8s0mQ2GKIYdDO42kuRxaqVqrh2TahtTQ DeHvsXWD9ZivyLsPP2cPrfcRhHVGjhOpnAu6E2gVglYI8L5kBeOhdkdF7NyIHCE16+ a5zjypcBX6vE5qs/Lv0EYy6aFU/RvxcL/edVsn3r695CfrtVLzE5ZixZJ7yRSkCZZ3 xj91p5dsHYcjo2FApj2Eyy7dD3bzfk3avOiu1CvosShMilzoG3i6t+04/kuIvDFVu3 OJDGaKacKGgbw== Date: Thu, 18 Jul 2024 16:59:50 +0100 From: Conor Dooley To: Heiko =?iso-8859-1?Q?St=FCbner?= Cc: mturquette@baylibre.com, sboyd@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org Subject: Re: [PATCH v2 1/3] dt-bindings: clocks: add binding for voltage-controlled-oscillators Message-ID: <20240718-prozac-specks-6b5fd8b83e3e@spud> References: <20240715110251.261844-1-heiko@sntech.de> <20240715110251.261844-2-heiko@sntech.de> <20240716-deceiving-saucy-851fb2303c1f@spud> <3178118.zE8UqtGg2D@diego> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="TA6tyFoqBwcLvbVt" Content-Disposition: inline In-Reply-To: <3178118.zE8UqtGg2D@diego> --TA6tyFoqBwcLvbVt Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jul 18, 2024 at 11:25:28AM +0200, Heiko St=FCbner wrote: > Hi Conor, >=20 > Am Dienstag, 16. Juli 2024, 18:15:08 CEST schrieb Conor Dooley: > > On Mon, Jul 15, 2024 at 01:02:49PM +0200, Heiko Stuebner wrote: > > > In contrast to fixed clocks that are described as ungateable, boards > > > sometimes use additional oscillators for things like PCIe reference > > > clocks, that need actual supplies to get enabled and enable-gpios to = be > > > toggled for them to work. > > >=20 > > > This adds a binding for such oscillators that are not configurable > > > themself, but need to handle supplies for them to work. > > >=20 > > > In schematics they often can be seen as > > >=20 > > > ---------------- > > > Enable - | 100MHz,3.3V, | - VDD > > > | 3225 | > > > GND - | | - OUT > > > ---------------- > > >=20 > > > or similar. The enable pin might be separate but can also just be tied > > > to the vdd supply, hence it is optional in the binding. > > >=20 > > > Signed-off-by: Heiko Stuebner > > > --- > > > .../bindings/clock/voltage-oscillator.yaml | 49 +++++++++++++++++= ++ > > > 1 file changed, 49 insertions(+) > > > create mode 100644 Documentation/devicetree/bindings/clock/voltage-o= scillator.yaml > > >=20 > > > diff --git a/Documentation/devicetree/bindings/clock/voltage-oscillat= or.yaml b/Documentation/devicetree/bindings/clock/voltage-oscillator.yaml > > > new file mode 100644 > > > index 0000000000000..8bff6b0fd582e > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/clock/voltage-oscillator.yaml > > > @@ -0,0 +1,49 @@ > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > > +%YAML 1.2 > > > +--- > > > +$id: http://devicetree.org/schemas/clock/voltage-oscillator.yaml# > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > + > > > +title: Voltage controlled oscillator > >=20 > > Voltage controlled oscillator? Really? That sounds far too similar to a > > VCO to me, and the input voltage here (according to the description at > > least) does not affect the frequency of oscillation. >=20 > That naming was suggested by Stephen in v1 [0] . I think "voltage-oscillator" is a confusing name, and having "voltage controlled oscillator" in the title doubly so as this isn't a binding for a VCO. A VCO is a more general case of the sort of device that you're talking about here, so a part of me can see it - but I think specific compatibles would be required for actual VCOs, since the "transfer function" would vary per device. > Of course the schematics for the board I have only describe it as > "100MHz,3.3V,3225" , thumbing through some mouser parts matching that > only mentions "supply voltage" in their datasheets but not a dependency > between rate and voltage. >=20 > [0] https://lore.kernel.org/linux-arm-kernel/b3c450a94bcb4ad0bc5b3c7ee871= 2cb8.sboyd@kernel.org/ >=20 > > Why the dedicated binding, rather than adding a supply and enable-gpio > > to the existing "fixed-clock" binding? I suspect that a large portion of > > "fixed-clock"s actually require a supply that is (effectively) > > always-on. >=20 > I guess there are three aspects: > - I do remember discussions in the past about not extending generic > bindings with device-specific stuff. FWIW, I wouldn't classify this as device-specific. "enable-gpios" and "vdd-supply" are pretty generic and I think the latter is missing from the vast majority of real* "fixed-clocks". I would expect that devices where the datasheet would call * Real because there's plenty of "fixed-clocks" (both in and out of tree) that are used to work around the lack of a clock-controller driver for an SoC. > I think generic power-sequences > were the topic back then, though that might have changed over time? > - There are places that describe "fixed-clock" as > "basic fixed-rate clock that cannot gate" [1] I think that that is something that could be changed, it's "just" a comment in some code! Sounds like Stephen disagrees though :) > - Stephen also suggested a separate binding [2] I liked your "gated-oscillator" suggestion in another reply, but "gated-fixed-clock" might be a better "thematic" fit since this is a special case of fixed-clocks? Cheers, Conor. > With the fixed-clock being sort of the root for everything else on most > systems, I opted to leave it alone. I guess if the consenus really is that > this should go there, I can move it, but discussion in v1=20 >=20 > Interestingly the fixed clock had a gpios property 10 years ago [3] :-) . heh! >=20 > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tr= ee/drivers/clk/clk-fixed-rate.c#n18 > [2] https://lore.kernel.org/linux-arm-kernel/68f6dc44a8202fd83792e58aea13= 7632.sboyd@kernel.org/ > [3] https://lore.kernel.org/linux-kernel//20140515064420.9521.47383@quant= um/T/#t --TA6tyFoqBwcLvbVt Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZpk79gAKCRB4tDGHoIJi 0ocpAQDlY1WVEOAb/tAnKL+v/4KqvF6yQjSSOa/QJ9Xn/KwzwQEA6xZbMOFj+ofl qMmgXTkeOunG/hACMIplnIyteyzFRwI= =RPQe -----END PGP SIGNATURE----- --TA6tyFoqBwcLvbVt--