Re: [PATCH 2/4] ARM: qcom: add description of KPSS WDT for IPQ8064

From: Josh Cartwright
Date: Wed Oct 01 2014 - 14:21:47 EST


Hey Stephen-

Thanks for taking a look.

On Wed, Oct 01, 2014 at 10:28:55AM -0700, Stephen Boyd wrote:
> On 10/01, Josh Cartwright wrote:
> > @@ -96,6 +104,13 @@
> > cpu-offset = <0x80000>;
> > };
> >
> > + watchdog@208a038 {
> > + compatible = "qcom,kpss-wdt-ipq8064";
> > + reg = <0x0208a038 0x40>;
>
> Not being aligned to 4k or 1k raises red flags.
>
> The watchdog is part of the timer block (on this chip it's
> "qcom,kpss-timer"). We should add qcom,kpss-wdt to the compatible
> list in the timer binding and extend that binding to have clocks
> and timeout-sec (watchdog-timeout-sec?).

Yeah, the description of this thing is a bit awkward.

I'm not sure how I'd feel about just just adding "qcom,kpss-wdt" to the
timer node compatible. I'm wondering if the WDT(s) should be a
subnode(s) of the timer node instead?

The percpu-ness of the two WDTs makes configuration even more
interesting, as it's possible you'd want to independently configure
timeouts for CPU0_WDT0 and CPU1_WDT0, supporting this with a coalesced
timer/wdt would be cumbersome.

Something like this perhaps:

timer@200a000 {
compatible = "qcom,kpss-timer", "qcom,msm-timer";
interrupts = <1 1 0x301>,
<1 2 0x301>,
<1 3 0x301>;
reg = <0x0200a000 0x100>;
clock-frequency = <25000000>,
<32768>;
cpu-offset = <0x80000>;

#address-cells = <1>;
#size-cells = <1>;
ranges;

cpu0_wdt0: watchdog@208a038 {
compatible = "qcom,kpss-wdt";
reg = <0x208a038 0x40>;
interrupts = <1 4 0x301>,
clocks = <&sleep_clk>;
timeout-sec = <10>;
cpu = <&cpu0>;
};

cpu0_wdt1: watchdog@208a060 {
compatible = "qcom,kpss-wdt";
reg = <0x208a060 0x40>;
interrupts = <1 5 0x301>,
clocks = <&sleep_clk>;
timeout-sec = <20>;
cpu = <&cpu0>;
};

cpu1_wdt0: watchdog@209a038 {
compatible = "qcom,kpss-wdt";
reg = <0x209a038 0x40>;
interrupts = <1 4 0x301>,
clocks = <&sleep_clk>;
timeout-sec = <8>;
cpu = <&cpu1>;
};

cpu1_wdt1: watchdog@209a060 {
compatible = "qcom,kpss-wdt";
reg = <0x209a060 0x40>;
interrupts = <1 5 0x301>,
clocks = <&sleep_clk>;
timeout-sec = <15>;
cpu = <&cpu1>;
};
};

> This would follow DT best practices of having one node per device. We
> could also add the interrupts too, even if they're not used by the
> driver right now.
>
> > + clocks = <&sleep_clk>;
> > + timeout-sec = <10>;
> > + };
> > +

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