From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 84549CCD184 for ; Tue, 14 Oct 2025 19:40:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=+8yIrhR2iOVuc/WhcMkGU3ZN0K5UGRgtG1whg0Gx32o=; b=zY6wcOX8im0GMz51jshdxpkvq1 /7vfMtGLXXX09PbadI+h+paA5HsIfSYPMpk+4GNnR0FmxzEG1Rp/qHG8Px/99zzBl0NqGj/4liZi6 odJj2IVQRf/0wjeHpjXzAbcntOkwFxShzoy2zP1BvUSTKxSEOeAVCe4di+CbQOhyMYjdCr1cTX+LD VIIAUDxKY8Qkqo0gdq65tc6ZqPictDvdRKYcbor8NcP5zneC/JKLPnIMrBjxxx3m5JK4dMxOm9+eW EXjomTxVhhx/1M4TdXzXyfclvRt3gvPE5i3mVpNrqcF4AKnZMirOtk41MWydGvYFGdRGV5qMNQglk oJj3yUnA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8ksQ-0000000HI3y-41CF; Tue, 14 Oct 2025 19:40:06 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8ksJ-0000000HHza-1Yfk for linux-arm-kernel@lists.infradead.org; Tue, 14 Oct 2025 19:40:05 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id F05A343ADB; Tue, 14 Oct 2025 19:39:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4D77C4CEE7; Tue, 14 Oct 2025 19:39:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760470798; bh=O5H/YsuZs738YLiu8CU7UPY57QeILHiPa3/g7uk/1NA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qSLN5Hq5qQqaeRoRL4S6gw3Nbz3N+rvUZnaplautiXAX6nefXQTlvHDiCM4jO2Dxb S5IWLDMMJS9ZSDIPTK2YHsMHutYxBoAxatnzI97AnabTbrkTEaHRYgBKH3RArkCPjA SGFbcnTfbjB+mobrDoGdydj5sZ46yN146NH3xWbjQh6Qn+RVITJ0r3LT5vF/AzLt87 gynvyfmfcWo5W1W1MTFLphm4t6YzZgdpKL3klZ1aRsYzb4eOXtKkah5YRJ8iNyId4f ZSXSMipjbBH6H0BhQjiPO8XHU97HxkESsQBDiI++fx+agiP7s158V8c2zSbVpfhUlc NdnPq0J/RJgsA== Date: Tue, 14 Oct 2025 20:39:53 +0100 From: Conor Dooley To: Linus Walleij Cc: Antonio Borneo , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Maxime Coquelin , Alexandre Torgue , Bartosz Golaszewski , linux-gpio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, Christophe Roullier , Fabien Dessenne , Valentin Caron Subject: Re: [PATCH v3 02/10] dt-bindings: pincfg-node: Add properties 'skew-delay-{in,out}put' Message-ID: <20251014-water-gown-11558c4eabe7@spud> References: <20251014140451.1009969-1-antonio.borneo@foss.st.com> <20251014140451.1009969-3-antonio.borneo@foss.st.com> <20251014-barbecue-crewman-717fe614daa6@spud> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="DnZFP0H7yz35f5cB" Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251014_123959_469147_BFB11BA5 X-CRM114-Status: GOOD ( 31.70 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --DnZFP0H7yz35f5cB Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Oct 14, 2025 at 09:33:14PM +0200, Linus Walleij wrote: > On Tue, Oct 14, 2025 at 8:04=E2=80=AFPM Conor Dooley w= rote: > > On Tue, Oct 14, 2025 at 04:04:43PM +0200, Antonio Borneo wrote: >=20 > > > + skew-delay-input: > > > + $ref: /schemas/types.yaml#/definitions/uint32 > > > + description: > > > + this affects the expected clock skew on input pins. > > > + Typically indicates how many double-inverters are used to > > > + delay the signal. > > > > This property seems to be temporal, I would expect to see a unit of time > > mentioned here, otherwise it'll totally inconsistent in use between > > devices, and also a standard unit suffix in the property name. > > pw-bot: changes-requested >=20 > Don't blame the messenger, the existing property skew-delay > says: >=20 > skew-delay: > $ref: /schemas/types.yaml#/definitions/uint32 > description: > this affects the expected clock skew on input pins > and the delay before latching a value to an output > pin. Typically indicates how many double-inverters are > used to delay the signal. >=20 > This in turn comes from the original > Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt > document, which in turn comes from this commit: >=20 > commit e0e1e39de490a2d9b8a173363ccf2415ddada871 > Author: Linus Walleij > Date: Sat Oct 28 15:37:17 2017 +0200 >=20 > pinctrl: Add skew-delay pin config and bindings >=20 > Some pin controllers (such as the Gemini) can control the > expected clock skew and output delay on certain pins with a > sub-nanosecond granularity. This is typically done by shunting > in a number of double inverters in front of or behind the pin. > Make it possible to configure this with a generic binding. >=20 > Cc: devicetree@vger.kernel.org > Acked-by: Rob Herring > Acked-by: Hans Ulli Kroll > Signed-off-by: Linus Walleij >=20 > So by legacy skew-delay is a custom format, usually the number of > (double) inverters. Yeah, I actually noticed this after sending the mail. But as you say below, the new properties can be done with a unit etc >=20 > I don't recall the reason for this way of defining things, but one reason > could be that the skew-delay incurred by two inverters is very > dependent on the production node of the silicon, and can be > nanoseconds or picoseconds, these days mostly picoseconds. > Example: Documentation/devicetree/bindings/net/adi,adin.yaml >=20 > Antonio, what do you say? Do you have the actual skew picosecond > values for the different settings so we could define this as >=20 > skew-delay-input-ps: > skew-delay-output-ps: >=20 > and translate it to the right register values in the driver? The patch for the specific binding does have values in units of seconds assigned to each register value, so I think this should be doable. >=20 > If we have the proper data this could be a good time to add this > ISO unit to these two props. >=20 > Yours, > Linus Walleij --DnZFP0H7yz35f5cB Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCaO6nCQAKCRB4tDGHoIJi 0qLlAP9810SKsRFfc73sjXKlJV1iLRHPiWHn2M7TKwMkhNAhNQEAoJHsRqsTrOZv DEfxbqgGD+nWjS0Kv0p8dpJZC6EYfw4= =BzPH -----END PGP SIGNATURE----- --DnZFP0H7yz35f5cB--