From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH] clk: clk_register: Correctly initialize enable_count To: =?UTF-8?Q?Emilio_L=c3=b3pez?= , Michael Turquette , Stephen Boyd References: <1455058120-7398-1-git-send-email-rklein@nvidia.com> <56BAA6D9.9090009@elopez.com.ar> CC: , From: Rhyland Klein Message-ID: <56BB82A8.8010701@nvidia.com> Date: Wed, 10 Feb 2016 13:34:16 -0500 MIME-Version: 1.0 In-Reply-To: <56BAA6D9.9090009@elopez.com.ar> Content-Type: text/plain; charset="windows-1252" Return-Path: rklein@nvidia.com List-ID: On 2/9/2016 9:56 PM, Emilio L=F3pez wrote: > Hi, >=20 > El 09/02/16 a las 19:48, Rhyland Klein escribi=F3: >> When clocks are registered, they could be enabled already in >> hardware. As of now, the enable count will start at 0. When this >> happens, it means a clock is enabled and the framework doesn't know >> that, so it will always report it as disabled. >=20 > Keep in mind that during the boot process, towards the end, unused > clocks get disabled, so the state remains in sync. If suddenly the > enable_count on unused clocks is not 0, this will break and unused > clocks will remain on, wasting power. Hmm, I had misread the logic in clk_disable_unused_subtree(), namely I inverted the check on enable_count when I was looking at it. It does seem like it would take care of the clocks I was referring to. >=20 > http://lxr.free-electrons.com/source/drivers/clk/clk.c#L244 >=20 > What issue were you having that prompted you to write this patch? I ran into the situation where a peripheral clock was enabled before the kernel loaded, and I was trying to disable it in the clk-tegra210 driver. Calling clk_disable() won't work, as the clock doesn't have an enable_count. I do think that the clk_disable_unused_subtree() should pick up the slack, but I was trying to disable it before the cleanup code to remove unused clocks ran. I think you are right and the clean up code should cover the situation I was looking at. Thanks. -rhyland --=20 nvpublic