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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95A4AC65BA7 for ; Fri, 5 Oct 2018 08:55:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 55A9B208E7 for ; Fri, 5 Oct 2018 08:55:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 55A9B208E7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728708AbeJEPxD (ORCPT ); Fri, 5 Oct 2018 11:53:03 -0400 Received: from mail-vs1-f65.google.com ([209.85.217.65]:33624 "EHLO mail-vs1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728012AbeJEPxC (ORCPT ); Fri, 5 Oct 2018 11:53:02 -0400 Received: by mail-vs1-f65.google.com with SMTP id e206so7068297vsd.0; Fri, 05 Oct 2018 01:55:16 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GrWov/l/OjpiCdqJJ7K6egXCU9G1/zgrl4TFJVgYDfA=; b=gfJ2KA/zQyQCALPkOOcTMtM9+DEW/Nh5vQT3coGQcgh/v/oboxu9Rq3iB6xl4o2JMg WQLOyIraQf2pevj4ImiS0eTdh5/hhSvQHuWi6sSBvQsg99GWvBey7wGE9AMnQPZLSAs6 /KUPi8BzxYbsEuMsploNWV/gts9wKxi448KrZwF7wET5d6V/BWz1hh+RyMJqrBnDcSit dwZotedBJvxaX/Ub3t5hnVjl+LQB1jvMK3dEZ0PY1T0MxGLZj2j4aZgc6KoMBtnRuZyK g7DSO5qxCbAHCN9GWynQR7yGSG3nEBZpePUwB/m2ieyiaI7yvE5om5ksMQBbfCrEcoWQ oQpA== X-Gm-Message-State: ABuFfoiuDn9DzYFluSQno0s5R3gfrFMkP3lqZZBq43oIfQJ6oypGY5nk Cu+WeDNLamRK+wx/Hlnf+wtF6+C5HvhDQe+YfeA= X-Google-Smtp-Source: ACcGV62XA51B25wZR70TbGEFzpE4UJHSbYcFHxg2OEQDopwIOtpna/a0aR7wzEc90MEur51BWxCV/0oILPeyCJJbw0w= X-Received: by 2002:a67:e015:: with SMTP id c21mr3666257vsl.63.1538729715568; Fri, 05 Oct 2018 01:55:15 -0700 (PDT) MIME-Version: 1.0 References: <20180927180038.24599-1-geert+renesas@glider.be> <1538648094.14153.8.camel@pengutronix.de> In-Reply-To: <1538648094.14153.8.camel@pengutronix.de> From: Geert Uytterhoeven Date: Fri, 5 Oct 2018 10:55:04 +0200 Message-ID: Subject: Re: [PATCH v2] reset: Exclusive resets must be dedicated to a single hardware block To: Philipp Zabel Cc: Geert Uytterhoeven , Auger Eric , Alex Williamson , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Linux-Renesas , Linux Kernel Mailing List , KVM list , Rob Herring , Mark Rutland Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Philipp, On Thu, Oct 4, 2018 at 12:15 PM Philipp Zabel wrote: > Thank you for the patch. I'd still like to hear the device tree > maintainers' (added to Cc:) opinion on parsing the whole DT for "resets" > phandle properties to find shared resets like this. > > On Thu, 2018-09-27 at 20:00 +0200, Geert Uytterhoeven wrote: > > In some SoCs multiple hardware blocks may share a reset control. > > The reset control API for shared resets will only assert such a reset > > when the drivers for all hardware blocks agree. > > The exclusive reset control API still allows to assert such a reset, but > > that impacts all other hardware blocks sharing the reset. > > > > While the kernel doc comments clearly state that the API for shared > > resets applies to reset controls which are shared between hardware > > blocks, the exact meaning of exclusive resets is not documented. > > Fix the semantic ambiguity with respect to exclusive access vs. > > exclusive reset lines by: > > 1. Clarifying that exclusive resets really are intended for use with > > reset controls which are dedicated to a single hardware block, > > 2. Ensuring that obtaining an exclusive reset control will fail if the > > reset is shared by multiple hardware blocks, for both DT-based and > > lookup-based reset controls. > > > > Signed-off-by: Geert Uytterhoeven > > --- > > This is v2 of "[RFC] reset: Add support for dedicated reset controls": > > - Fix wrong variable in __reset_is_dedicated() loop, > > - Add missing of_node_put() in __of_reset_is_dedicated(), > > - Document that exclusive reset controls imply they are dedicated to a > > single hardware block, > > - Drop new dedicated flag and new API reset_control_get_dedicated(), > > as exclusive already implies dedicated, > > - Rename {__of_,}reset_is_dedicated() to {__of_,}reset_is_exclusive(), > > - Reword description. > > > > Note: Exclusive lookup-based reset controls were not tested. > > --- > > drivers/reset/core.c | 58 +++++++++++++++++++++++++++++++++++++++++++ > > include/linux/reset.h | 5 +++- > > 2 files changed, 62 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/reset/core.c b/drivers/reset/core.c > > index 225e34c56b94a2e3..2f5b61226c7964eb 100644 > > --- a/drivers/reset/core.c > > +++ b/drivers/reset/core.c > > @@ -459,6 +459,38 @@ static void __reset_control_put_internal(struct reset_control *rstc) > > kref_put(&rstc->refcnt, __reset_control_release); > > } > > > > +static bool __of_reset_is_exclusive(const struct device_node *node, > > + const struct of_phandle_args args) Oops, this should take *args, not args. > > +{ > > + struct of_phandle_args args2; > > + struct device_node *node2; > > + int index, ret; > > + bool eq; > > I suppose it is very unlikely to get false positives where an arbitrary > node contains a "resets" property that looks like a proper phandle to an > actual reset-controller node. > Are we allowed though to scan the whole tree for "resets" properties > regardless of the nodes' bindings or compatible properties like this? Given "resets" is a more-or-less standard property, I'd say yes. Especially given of_parse_phandle_with_args() does verify that the target node has #reset-cells, and that the number of parameters matches that. > > + for_each_node_with_property(node2, "resets") { > > + if (node == node2) > > + continue; > > + > > + for (index = 0; ; index++) { > > + ret = of_parse_phandle_with_args(node2, "resets", > > + "#reset-cells", index, > > + &args2); > > + if (ret) > > + break; > > + > > + eq = (args2.np == args.np && > > + args2.args_count == args.args_count && > > + !memcmp(args2.args, args.args, > > + args.args_count * sizeof(args.args[0]))); As there's at least one other function in -next that compares of_phandle_args, I will add a helper of_phandle_args_eq(). > > + of_node_put(args2.np); > > + if (eq) > > Emitting a loud warning here could be very helpful if it contains > both the reset controller node and the reset index, as well as the > consumer nodes: node and node2. Indeed, will do, also for lookup resets. We already have of_print_phandle_args(), but that is a bit inflexible. Adding support for "%pOFa" looks like the modern thing to do. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds