From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750959AbbCBIQP (ORCPT ); Mon, 2 Mar 2015 03:16:15 -0500 Received: from mail-wg0-f49.google.com ([74.125.82.49]:33407 "EHLO mail-wg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750758AbbCBIQN (ORCPT ); Mon, 2 Mar 2015 03:16:13 -0500 Date: Mon, 2 Mar 2015 08:16:06 +0000 From: Lee Jones To: Maxime Coquelin Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mturquette@linaro.org, sboyd@codeaurora.org, kernel@stlinux.com, devicetree@vger.kernel.org Subject: Re: [STLinux Kernel] [PATCH 3/4] clk: Provide always-on clock support Message-ID: <20150302081606.GC31325@x1> References: <1425071674-16995-1-git-send-email-lee.jones@linaro.org> <1425071674-16995-4-git-send-email-lee.jones@linaro.org> <54F173B7.9030305@st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <54F173B7.9030305@st.com> 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 On Sat, 28 Feb 2015, Maxime Coquelin wrote: > Hi Lee, > > On 02/27/2015 10:14 PM, Lee Jones wrote: > >Lots of platforms contain clocks which if turned off would prove fatal. > >The only way to recover from these catastrophic failures is to restart > >the board(s). Now, when a clock is registered with the framework it is > >compared against a list of provided always-on clock names which must be > >kept ungated. If it matches, we enable the existing CLK_IGNORE_UNUSED > >flag, which will prevent the common clk framework from attempting to > >gate it during the clk_disable_unused() procedure. > > Please correct me if I'm wrong, but your patch does not fix the > issue you had initially. > Let's take an example: > A clock is critical for the system, and should never be gated, so > you add the CLK_IGNORE_UNUSED > flag so that it is not disabled by clk_disable_unused() procedure. > The same clock is also used by other IPs, for example spi 0 instance. > When starting a spi transfer, clk_enable() is called on this clock, > so its usecount becomes 1. > Once transfer done, clk_disable() is called, usecount becomes 0 and > the clock gets disabled: system freeze. You're right. I also need to extend clk_core_disable() to take notice of CLK_IGNORE_UNUSED. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog