From: robherring2@gmail.com (Rob Herring)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 4/4] clk: dt: Introduce always-on clock domain documentation
Date: Wed, 18 Feb 2015 10:54:20 -0600 [thread overview]
Message-ID: <CAL_Jsq+r1BKt5B9FNPG+Y0Oi1-3RGNmRUDbpX_uDJwr45bxMXA@mail.gmail.com> (raw)
In-Reply-To: <1424276101-30137-5-git-send-email-lee.jones@linaro.org>
On Wed, Feb 18, 2015 at 10:15 AM, Lee Jones <lee.jones@linaro.org> wrote:
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
> .../devicetree/bindings/clock/clk-domain.txt | 35 ++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/clock/clk-domain.txt
>
> diff --git a/Documentation/devicetree/bindings/clock/clk-domain.txt b/Documentation/devicetree/bindings/clock/clk-domain.txt
> new file mode 100644
> index 0000000..b86772f5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/clk-domain.txt
> @@ -0,0 +1,35 @@
> +Always-on Clock Domain
> +
> +Some hardware is contains bunches of clocks which must never be
> +turned off. If drivers a) fail to obtain a reference to any of
> +these or b) give up a previously obtained reference during suspend,
> +the common clk framework will attempt to disable them and the
> +hardware can fail irrecoverably. Usually, the only way to recover
> +from these failures is to restart.
How is (b) not a bug?
While I think we need something here, I worry that this will be abused
to be a list of clocks you have not gotten around to managing. We
cannot be changing the DT every time the kernel starts managing a
clock. I think this should operate more as always on until claimed.
But then you get into drivers having to be aware that the clock
started enabled.
Also, I feel like we are using DT to work around kernel policy (of
turning off clocks). If the policy was to leave on clocks, then we
would be trying to put a list of clocks to disable in DT.
Rob
> +
> +To avoid either of these two scenarios from catastrophically
> +disabling an otherwise perfectly healthy running system, we have
> +implemented a clock domain where clocks are consumed and references
> +are taken, thus preventing them from being shut down by the
> +framework.
> +
> +We use the generic clock bindings found in:
> + Documentation/devicetree/bindings/clock/clock-bindings.txt
> +
> +Required properties:
> +- compatible : Must be "always-on-clk-domain"
> +
> +Example:
> +
> +clk-domain {
> + compatible = "always-on-clk-domain";
> + clocks = <&clk_s_c0_flexgen CLK_EXT2F_A9>,
> + <&clk_s_c0_flexgen CLK_COMPO_DVP>,
> + <&clk_s_c0_flexgen CLK_MMC_1>,
> + <&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>,
> + <&clk_s_a0_flexgen CLK_IC_LMI0>,
> + <&clk_m_a9>;
> +};
> --
> 1.9.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2015-02-18 16:54 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 [this message]
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
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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