Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752833AbbBSK2R (ORCPT ); Thu, 19 Feb 2015 05:28:17 -0500 Received: from mail-we0-f176.google.com ([74.125.82.176]:36758 "EHLO mail-we0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752643AbbBSK2O (ORCPT ); Thu, 19 Feb 2015 05:28:14 -0500 Date: Thu, 19 Feb 2015 10:28:10 +0000 From: Lee Jones To: Geert Uytterhoeven 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" Subject: Re: [PATCH v2 4/4] clk: dt: Introduce always-on clock domain documentation Message-ID: <20150219102810.GE12212@x1> References: <1424276101-30137-5-git-send-email-lee.jones@linaro.org> <20150218171230.GA30676@x1> <20150218215435.GA32415@x1> <20150219094200.GB12212@x1> <20150219101106.GD12212@x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2810 Lines: 65 On Thu, 19 Feb 2015, Geert Uytterhoeven wrote: > Hi Lee, > > On Thu, Feb 19, 2015 at 11:11 AM, Lee Jones wrote: > > On Thu, 19 Feb 2015, Geert Uytterhoeven wrote: > >> 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? > > > > So instead of this nice succinct, simple, cover all bases > > (interconnects was just an example, there are bound to be others), > > generic framework, you are suggesting to write drivers for devices > > which other than "don't turn my clocks off", Linux can't actually see > > or control? > > DT describes the hardware, not behavior. Okay so ... /* * ICNs are not visible/controllable in Linux, but references to their * clocks must be obtained and retained or the platform will become * irrecoverably unresponsive. */ interconnects@0 { compatible = "always-on-clk-domain"; clocks = <&clk_s_c0_flexgen CLK_ICN_SBC>, <&clk_s_c0_flexgen CLK_ICN_LMI>, <&clk_s_c0_flexgen CLK_ICN_CPU>, <&clk_s_c0_flexgen CLK_TX_ICN_DMU>; }; -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/