Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752937AbbBSJzU (ORCPT ); Thu, 19 Feb 2015 04:55:20 -0500 Received: from mail-ob0-f176.google.com ([209.85.214.176]:64062 "EHLO mail-ob0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752481AbbBSJzS (ORCPT ); Thu, 19 Feb 2015 04:55:18 -0500 MIME-Version: 1.0 In-Reply-To: <20150219094200.GB12212@x1> References: <1424276101-30137-1-git-send-email-lee.jones@linaro.org> <1424276101-30137-5-git-send-email-lee.jones@linaro.org> <20150218171230.GA30676@x1> <20150218215435.GA32415@x1> <20150219094200.GB12212@x1> Date: Thu, 19 Feb 2015 10:55:16 +0100 X-Google-Sender-Auth: c_XU9kxxZQ0tVSkWWN30OL1r8Yc Message-ID: Subject: Re: [PATCH v2 4/4] clk: dt: Introduce always-on clock domain documentation From: Geert Uytterhoeven To: Lee Jones Cc: Rob Herring , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Mike Turquette , Stephen Boyd , kernel@stlinux.com, "devicetree@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1902 Lines: 43 Hi Lee, On Thu, Feb 19, 2015 at 10:42 AM, Lee Jones wrote: >> What kind of clocks are these? What do they control? >> Memory controllers? Bus controllers? >> >> They must control some device(s), so there should be one or more device >> nodes in DT that reference these clocks. >> As soon as that information is in DT, support can be added to Linux to >> make sure the "critical" clocks stay enabled, either through a real driver, >> or through platform code. > > Some do, some don't. For instance, we have one clock which controls > SPI and I2C that must not be turned off. We discovered this then when > a suspend was attempted and the board refused to resume. This clock > also runs one of the critical interconnects that runs from the a9. It > would be wrong to remove the clk_disable() attempt from the SPI/I2C > drivers because the same IP on another board might be controlled by a > different clock which is able to be gated. > > There are also clocks which control other interconnects that are not > connected to any device drivers. If we fail to take references for > them before clk_disable_unused() is called, again the board hangs. We > even lose JTAG support. Interconnects are buses. Can't you represent those buses in the DT hierarchy, and give them clocks properties? 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/