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

[Павел]

чт, 16 мая 2019 г., 15:22 Sven Eckelmann <sven at narfation.org>:

> 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.
>

Okay, here what I've found in oem firmware (Zyxel nbg6617)

There are 2 clocks related to timer in oem firmware:
1. gcc_sleep_clk_src - 32.000
 ^---USB3 sleep clock
 ^---USB2 sleep clock
2. wifi_rtc_clk_src - 32.768
 ^---wcnssN sleep clock
 ^---wcnssN sleep clock

In upstream we don't have wifi_rtc clk and all mentioned childs are
connected to sleep clk.

So sleep clock at 32000 rate looks like some kind of a workaround and not
to break wifi they introduced a separate clock for that, the one that
really represents the hardware.

I'll drop the sleep clock rate change in the next version of patchset since
we don't need that kind of workaround for now.


> 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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