From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [STLinux Kernel] [PATCH 3/4] clk: Provide always-on clock support Date: Mon, 2 Mar 2015 08:16:06 +0000 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-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <54F173B7.9030305-qxv4g6HH51o@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Maxime Coquelin Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mturquette-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, sboyd-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, kernel-F5mvAk5X5gdBDgjK7y7TUQ@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org On Sat, 28 Feb 2015, Maxime Coquelin wrote: > Hi Lee, >=20 > On 02/27/2015 10:14 PM, Lee Jones wrote: > >Lots of platforms contain clocks which if turned off would prove fat= al. > >The only way to recover from these catastrophic failures is to resta= rt > >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_UNUS= ED > >flag, which will prevent the common clk framework from attempting to > >gate it during the clk_disable_unused() procedure. >=20 > 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. --=20 Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org =E2=94=82 Open source software for ARM SoCs =46ollow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html