DTS: clock not found

[Matthias Brugger]

Hi Javier,

2014-02-06 Javier Martinez Canillas <martinez.javier at gmail.com>:
> Hello Matthias,
>
> On Wed, Feb 5, 2014 at 6:02 PM, Matthias Brugger <matthias.bgg at gmail.com> wrote:
>> Hi,
>>
>> I'm stuck with dts problem. Whenever I try to find a clock for my
>> device, the of_get_clk returns an error "Kernel panic - not syncing:
>> Can't get timer clock"
>>
>> My DTS looks like this (reduced to relevant parts for easier reading):
>>
>
> Could you give more details about your platform?
>
> I would take a look to Documentation/devicetree/bindings/clock/<your
> platform>-clock.txt to be sure that you are using the bindings
> correctly.
>

This is part of some effort to port Linux to a new SoC, so no
documentation up to now...
Anyway I found the error.

I forgot to add my SoC to arch/arm/Makefile so that my SoC specific
init funtion weren't called.
So my device tree wasn't populated and therefore the clock had no properties.

>> #include <dt-bindings/interrupt-controller/irq.h>
>> #include <dt-bindings/interrupt-controller/arm-gic.h>
>> #include "skeleton.dtsi"
>>
>> / {
>>
>> [...]
>>
>>     soc {
>>         #address-cells = <1>;
>>         #size-cells = <1>;
>>         compatible = "simple-bus";
>>         ranges;
>>
>>         gic: interrupt-controller at 10212000 {
>>             compatible = "arm,cortex-a9-gic";
>>             interrupt-controller;
>>             #interrupt-cells = <3>;
>>             reg = <0x10211000 0x1000>,
>>                   <0x10212000 0x1000>;
>>         };
>>
>>        osc: oscillator {
>>             compatible = "fixed-clock";
>>             #clock-cells = <1>;
>
> Looking at Documentation/devicetree/bindings/clock/fixed-clock.txt it says:
>
> #clock-cells : from common clock binding; shall be set to 0

Yes, you are right.

>
> while your are setting your clock-cells to 1.
>
>>             clock-frequency  = <15000000>;
>>             clock-output-names = "osc";
>>         };
>>
>>         timer: timer-mysoc {
>>             compatible = "mysoc,mysoc-timer";
>>             reg = <0x10008000 0x30>;
>>             interrupts = <GIC_SPI 113 IRQ_TYPE_EDGE_RISING>;
>>             clocks = <&osc 0>;
>>             clock-names = "system15m";
>>         };
>>     };
>
> Documentation/devicetree/bindings/clock/clock-bindings.txt also says:
>
> ==Clock consumers==
>
> Required properties:
> clocks:         List of phandle and clock specifier pairs, one pair
>                 for each clock input to the device.  Note: if the
>                 clock provider specifies '0' for #clock-cells, then
>                 only the phandle portion of the pair will appear.
>
> So my educated guess is that you should use #clock-cells = <0>; your
> your clock provider device node and clocks = <&osc> on your clock
> consumer device node.

Thats true.

>
> By looking at DTS and DTSI that uses the fixed-clock binding I see
> that all platforms don't have their clocks providers device nodes
> under soc {} but on a separate clocks {} node. I didn't find on the
> clock-bindings.txt DT bindings documentation that this is a
> requirement so probably that is not issue in your case but still
> something to keep in mind.
>

The code I posted is nearly similar to the example in
Documentation/devicetree/bindings/clock/clock-bindings.txt.
Anyway it seems that of_clk_get searches for the "#clock-cells" cells
in the list "clocks". I suppose that the "clocks" list is populated by
the node present under clocks {}.

Thanks a lot for your hints.
Matthias

>> };
>>
>>
>> my /drivers/clocksource/mysoc-timer.c looks like this (reduced to
>> relevant parts for easier reading):
>>
>> [...]
>>
>> static void __init mysoc_timer_init(struct device_node *node)
>> {
>>     unsigned long rate = 0;
>>     struct clk *clk;
>>     int ret, irq;
>>     u32 val;
>>
>>     gpt_base = of_iomap(node, 0);
>>     if (!gpt_base)
>>         panic("Can't map registers");
>>
>>     irq = irq_of_parse_and_map(node, 0);
>>     if (irq <= 0)
>>         panic("Can't parse IRQ");
>>
>>     clk = of_clk_get(node, 0);
>>     if (IS_ERR(clk))
>>         panic("Can't get timer clock");
>>     clk_prepare_enable(clk);
>>
>>     rate = clk_get_rate(clk);
>>
>> }
>> CLOCKSOURCE_OF_DECLARE(mtk_mt6589, "mysoc,mysoc-timer",
>>             mysoc_timer_init);
>>
>>
>> What I'm missing? I seems as if the clock "osc" is not found in the
>> device tree. Any idea why. Building the DTB works without errors, but
>> I suppose that doesn't mean too much anyway.
>>
>> Cheers,
>> Matthias
>>
>> --
>> motzblog.wordpress.com
>
> Hope it helps,
>
> Javier



-- 
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