Re: [OpenWrt-Devel] [PATCH 2/4] ipq40xx: fix sleep clock

Re: [OpenWrt-Devel] [PATCH 2/4] ipq40xx: fix sleep clock

[Sven Eckelmann]

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On Tuesday, 14 May 2019 15:42:18 CEST Pavel Kubelun wrote:
> +--- a/arch/arm/boot/dts/qcom-ipq4019.dtsi
> ++++ b/arch/arm/boot/dts/qcom-ipq4019.dtsi
> +@@ -141,9 +141,9 @@
> +       };
> + 
> +       clocks {
> +-              sleep_clk: sleep_clk {
> ++              sleep_clk: gcc_sleep_clk_src {
> +                       compatible = "fixed-clock";
> +-                      clock-frequency = <32768>;
> ++                      clock-frequency = <32000>;
> +                       #clock-cells = <0>;
> +               };

On Thursday, 16 May 2019 13:18:14 CEST Павел wrote:
[...]
> > And maybe some of these guys also know how to find the ipq40xx clock
> > controller reference or hardware reference. Because I was only able to
> > verify
> > for IPQ8072 that it had a 32.768 KHz sleep clock. But the
> >
> 
> If you are completely sure about that, then I guess that they have
> (un)intentionally messed with the clock in QSDK, because they state that
> ipq807x has the same 32000 khz crystal.
> https://source.codeaurora.org/quic/qsdk/oss/kernel/linux-msm/tree/arch/arm64/boot/dts/qcom/qcom-ipq807x-soc.dtsi?h=eggplant#n2055

Confidence is the wrong word. I can only state that this is written in 
80-YA727-13 Rev. D (IPQ8072.AP.HK07). Same for other devices like 
IPQ8078 AP.HK02, IPQ8074 AP.HK01, ...

But I found in the same document that they call it the "32 KHz sleep clock in" 
in one section and and in another table "32.768 KHz sleep clock input to the 
IPQ8072" (next to the name "...32K..."). So it is now to the reader to find 
out what they meant here in which reference document. So maybe they also meant 
32.768 KHz when in the IPQ4019 Watchdog document when they wrote 32 Khz sleep 
clock... who knows.

My gut feeling (sorry, not an HW guy) tell me that they are just using a 
32.768 KHz clock (from a standard 32.768 KHz oscillator) in all these products 
and just shortened it to 32K at some point in the document. And now Gopinath 
Sekar wrote 32000 instead of 32768. But I absolutely don't know what actually 
is there in HW.

Kind regards,
	Sven

[1] https://source.codeaurora.org/quic/qsdk/oss/kernel/linux-msm/commit/?id=d92ec59973484acc86dd24b67f10f8911b4b4b7d

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