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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D543C433F5 for ; Fri, 11 Mar 2022 22:43:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229701AbiCKWok (ORCPT ); Fri, 11 Mar 2022 17:44:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229636AbiCKWoa (ORCPT ); Fri, 11 Mar 2022 17:44:30 -0500 Received: from thorn.bewilderbeest.net (thorn.bewilderbeest.net [IPv6:2605:2700:0:5::4713:9cab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D782D277498; Fri, 11 Mar 2022 14:20:03 -0800 (PST) Received: from hatter.bewilderbeest.net (174-21-187-98.tukw.qwest.net [174.21.187.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: zev) by thorn.bewilderbeest.net (Postfix) with ESMTPSA id 075505DB; Fri, 11 Mar 2022 13:48:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bewilderbeest.net; s=thorn; t=1647035306; bh=P5ZzCyWn8Nc/M66e9melDdZzKd2Hn269uTStfhzFeC8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SeBg6gzwol1DPY+p8aBXLrgBeFwTV/cLJNNB+CzisLZn5BmXq8SHYUi4BmZTI5U87 EwF40TMiZh3r0gEjiam4MJxKeWQSKEJyhstMlz6G6s6e5q1orIIbmJ+LmDI+adDj6J dD4rHas3tEoq254WVvMBjHQvd6oLPDMmrV61sYro= Date: Fri, 11 Mar 2022 13:48:22 -0800 From: Zev Weiss To: Rob Herring Cc: devicetree@vger.kernel.org, openbmc@lists.ozlabs.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Arnd Bergmann , Mark Brown , Liam Girdwood Subject: Re: [PATCH v2 1/2] dt-bindings: Add power-efuse binding Message-ID: References: <20220308011811.10353-1-zev@bewilderbeest.net> <20220308011811.10353-2-zev@bewilderbeest.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 11, 2022 at 07:24:41AM PST, Rob Herring wrote: >On Mon, Mar 07, 2022 at 05:18:09PM -0800, Zev Weiss wrote: >> This can be used to describe a power output supplied by a regulator >> device that the system controls. >> >> Signed-off-by: Zev Weiss >> --- >> .../devicetree/bindings/misc/power-efuse.yaml | 49 +++++++++++++++++++ >> 1 file changed, 49 insertions(+) >> create mode 100644 Documentation/devicetree/bindings/misc/power-efuse.yaml >> >> diff --git a/Documentation/devicetree/bindings/misc/power-efuse.yaml b/Documentation/devicetree/bindings/misc/power-efuse.yaml >> new file mode 100644 >> index 000000000000..5f8f0b21af0e >> --- /dev/null >> +++ b/Documentation/devicetree/bindings/misc/power-efuse.yaml >> @@ -0,0 +1,49 @@ >> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) >> +%YAML 1.2 >> +--- >> +$id: http://devicetree.org/schemas/misc/power-efuse.yaml# >> +$schema: http://devicetree.org/meta-schemas/core.yaml# >> + >> +title: Generic power efuse device >> + >> +maintainers: >> + - Zev Weiss >> + >> +description: | >> + This binding describes a physical power output supplied by a >> + regulator providing efuse functionality (manual on/off control, and >> + auto-shutoff if current, voltage, or thermal limits are exceeded). >> + >> + These may be found on systems such as "smart" network PDUs, and >> + typically supply power to devices entirely separate from the system >> + described by the device-tree by way of an external connector such as >> + an Open19 power cable: >> + >> + https://www.open19.org/marketplace/coolpower-cable-assembly-8ru/ > >Not really a helpful link... > >I still don't understand what the h/w looks like here. At least I now >understand we're talking a fuse on power rail, not efuses in an SoC >used as OTP bits or feature disables. > The systems this would actually be used for would be things like these: - https://www.open19.org/marketplace/delta-16kw-power-shelf/ - https://www.open19.org/marketplace/inspur-open19-power-shelf-ob19200l1/ The rightmost pictures on those pages show the four black connectors where the cable assembly linked in the patch plugs in, each of which provides the outputs from 12 such efuses, on 12 pairs of ground and +12VDC pins. (There are also two more single outputs off to the side.) It essentially just amounts to an external power output supplied by a regulator, with the regulator providing an on/off switch, overcurrent protection, etc. And yes, the ambiguity of the "efuse" terminology is unfortunate (the "power-" prefix was an attempt to clarify it slightly). That's the term used in the documentation for the hardware and hence is what I've called it here, but I'd be open to using a different name if that would help. >> + >> +properties: >> + compatible: >> + const: power-efuse >> + >> + vout-supply: >> + description: >> + phandle to the regulator providing power for the efuse > >Vout is a supply to the efuse and not the rail being fused? Yeah, that was a fairly muddled description -- it's really the latter. Perhaps: phandle to the regulator providing power for the output rail controlled by the efuse ? > >Sorry, I know nothing about how an efuse is implemented so you are going >to have to explain or draw it. > >> + >> + error-flags-cache-ttl-ms: >> + description: >> + The number of milliseconds the vout-supply regulator's error >> + flags should be cached before re-fetching them. > >How does one fetch/read? the error flags? > In the specific case I'm dealing with, via PMBus STATUS_* commands, though I was aiming to keep this more generic so it could potentially be used to describe non-PMBus arrangements (in the Linux case, via whatever mechanism the implementation of the regulator's .get_error_flags() function uses). >> + >> +required: >> + - compatible >> + - vout-supply >> + >> +additionalProperties: false >> + >> +examples: >> + - | >> + efuse { >> + compatible = "power-efuse"; >> + vout-supply = <&efuse_reg>; >> + error-flags-cache-ttl-ms = <500>; >> + }; >> -- >> 2.35.1 >> >>