From: maxime.coquelin@st•com (Maxime Coquelin)
To: linux-arm-kernel@lists•infradead.org
Subject: [STLinux Kernel] [PATCH 3/4] clk: Provide always-on clock support
Date: Sat, 28 Feb 2015 08:52:23 +0100 [thread overview]
Message-ID: <54F173B7.9030305@st.com> (raw)
In-Reply-To: <1425071674-16995-4-git-send-email-lee.jones@linaro.org>
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.
BR,
Maxime
next prev parent reply other threads:[~2015-02-28 7:52 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-27 21:14 [PATCH 0/4] clk: Provide support for always-on clocks Lee Jones
2015-02-27 21:14 ` [PATCH 1/4] ARM: sti: stih407-family: Supply defines for CLOCKGEN A0 Lee Jones
2015-02-27 21:14 ` [PATCH 2/4] ARM: sti: stih410-clocks: Identify critical clocks as always-on Lee Jones
2015-04-02 8:00 ` [STLinux Kernel] " Peter Griffin
2015-02-27 21:14 ` [PATCH 3/4] clk: Provide always-on clock support Lee Jones
2015-02-27 21:51 ` Lee Jones
2015-02-28 7:52 ` Maxime Coquelin [this message]
2015-03-02 8:16 ` [STLinux Kernel] " Lee Jones
2015-04-01 1:13 ` Michael Turquette
2015-02-28 9:21 ` Jassi Brar
2015-03-02 8:36 ` Lee Jones
2015-03-02 10:08 ` Jassi Brar
2015-03-02 10:18 ` Lee Jones
2015-03-02 10:25 ` [STLinux Kernel] " Maxime Coquelin
2015-03-02 10:32 ` Lee Jones
2015-03-02 10:28 ` Jassi Brar
2015-03-02 10:40 ` Lee Jones
2015-04-01 1:42 ` Michael Turquette
2015-04-02 4:39 ` Jassi Brar
2015-04-02 7:10 ` Lee Jones
2015-02-27 21:14 ` [PATCH 4/4] clk: dt: Introduce binding for " Lee Jones
2015-04-02 8:12 ` [STLinux Kernel] [PATCH 0/4] clk: Provide support for always-on clocks Peter Griffin
2015-04-02 9:45 ` Gabriel Fernandez
2015-04-02 10:53 ` Lee Jones
2015-04-02 10:58 ` Lee Jones
2015-04-02 10:52 ` Lee Jones
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