From: lee.jones@linaro.org (Lee Jones)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 4/4] clk: dt: Introduce always-on clock domain documentation
Date: Thu, 19 Feb 2015 10:28:10 +0000 [thread overview]
Message-ID: <20150219102810.GE12212@x1> (raw)
In-Reply-To: <CAMuHMdW=kV+zx=Uq7y7SyrH3eQyWsdfWjuLFMAKQjPhX-QaPPA@mail.gmail.com>
On Thu, 19 Feb 2015, Geert Uytterhoeven wrote:
> Hi Lee,
>
> On Thu, Feb 19, 2015 at 11:11 AM, Lee Jones <lee.jones@linaro.org> wrote:
> > On Thu, 19 Feb 2015, Geert Uytterhoeven wrote:
> >> On Thu, Feb 19, 2015 at 10:42 AM, Lee Jones <lee.jones@linaro.org> 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 at 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
next prev parent reply other threads:[~2015-02-19 10:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-18 16:14 No subject Lee Jones
2015-02-18 16:14 ` [PATCH v2 1/4] ARM: sti: stih407-family: Supply defines for CLOCKGEN A0 Lee Jones
2015-02-18 16:14 ` [PATCH v2 2/4] ARM: sti: stih407-family: Provide Clock Domain information Lee Jones
2015-02-18 16:15 ` [PATCH v2 3/4] clk: Provide an always-on clock domain framework Lee Jones
2015-02-23 10:34 ` [STLinux Kernel] " Peter Griffin
2015-02-23 17:23 ` Mike Turquette
2015-02-24 11:04 ` Lee Jones
2015-02-25 15:24 ` Rob Herring
2015-02-25 15:48 ` Lee Jones
2015-02-25 18:26 ` Mike Turquette
2015-02-25 18:23 ` Mike Turquette
2015-02-18 16:15 ` [PATCH v2 4/4] clk: dt: Introduce always-on clock domain documentation Lee Jones
2015-02-18 16:54 ` Rob Herring
2015-02-18 17:12 ` Lee Jones
2015-02-18 18:50 ` Rob Herring
2015-02-18 21:54 ` Lee Jones
2015-02-18 23:45 ` Rob Herring
2015-02-19 10:05 ` Lee Jones
2015-02-19 9:27 ` Geert Uytterhoeven
2015-02-19 9:42 ` Lee Jones
2015-02-19 9:55 ` Geert Uytterhoeven
2015-02-19 10:11 ` Lee Jones
2015-02-19 10:18 ` Geert Uytterhoeven
2015-02-19 10:28 ` Lee Jones [this message]
2015-02-19 10:35 ` Geert Uytterhoeven
2015-02-19 10:43 ` Lee Jones
2015-02-19 11:01 ` Geert Uytterhoeven
2015-02-19 11:13 ` Lee Jones
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