Re: [PATCH] ARM: dts: Update arch timer node with clock frequency

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On Tue, Oct 8, 2013 at 5:15 PM, Olof Johansson <olof@xxxxxxxxx> wrote:
> [Adding Tony, who reported a mainline booting issue, and Sean who
> helped me track this down]
>
> On Mon, Sep 23, 2013 at 7:15 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote:
>> On Sat, Sep 21, 2013 at 04:24:59PM +0100, Tomasz Figa wrote:
>>> Hi Yuvaraj,
>>>
>>> On Wednesday 18 of September 2013 15:41:53 Yuvaraj Kumar C D wrote:
>>> > Without the "clock-frequency" property in arch timer node, could able
>>> > to see the below crash dump.
>>> [snip]
>>> > diff --git a/arch/arm/boot/dts/exynos5250.dtsi
>>> > b/arch/arm/boot/dts/exynos5250.dtsi index 7d7cc77..668ce5d 100644
>>> > --- a/arch/arm/boot/dts/exynos5250.dtsi
>>> > +++ b/arch/arm/boot/dts/exynos5250.dtsi
>>> > @@ -96,6 +96,7 @@
>>> >                          <1 14 0xf08>,
>>> >                          <1 11 0xf08>,
>>> >                          <1 10 0xf08>;
>>> > +           clock-frequency = <24000000>;
>>>
>>> Shouldn't it rather come from some clock provided by some clock controller
>>> instead?
>>>
>>> The frequency would be then retrieved using clk_get_rate() on a clock
>>> received by clk_get(), specified in device tree using generic clock
>>> bindings.
>>
>> If the bootloader has initialised the generic timer correctly, the
>> CNTFRQ register should contain the clock frequency, independent of any
>> external clock.
>
> So, we just sat here to bisect a problem on the Samsung Chromebook
> where we hit exactly this problem. The read-only firmware on the
> device does not set CNTFRQ at boot, so this fails.
>
> Apparantly the u-boot that comes with Arndale sets it, so I haven't
> seen this error on that platform.
>
>> Having the bootloader set CNTFRQ is by far the preferable solution, it
>> is architected for this purpose.
>
> Unfortunately there is now real hardware out there that needs this due
> to firmware bugs / missing features, so there's little other choice.
> :(
>
> I'll pick this patch up in the fixes branch for 3.12, unless someone
> complains loudly.

Perhaps the subject should say something about this only applying to exynos.

Rob
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