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From: Christian Lamparter <chunkeey@gmail.com>
To: Sricharan R <sricharan@codeaurora.org>
Cc: "Rob Herring" <robh+dt@kernel.org>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	agross@kernel.org, devicetree <devicetree@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-clk@vger.kernel.org,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
	"linux-arm Mailing List" <linux-arm-kernel@lists.infradead.org>,
	Павел <be.dissent@gmail.com>
Subject: Re: [PATCH 5/6] arm64: dts: Add ipq6018 SoC and CP01 board support
Date: Fri, 14 Jun 2019 22:41:15 +0200
Message-ID: <1981742.H2rzviYcjI@debian64> (raw)
In-Reply-To: <1a00e8c8-d07c-3b02-8ea5-6d5f3e2c7b1a@codeaurora.org>

On Wednesday, June 12, 2019 11:48:48 AM CEST Sricharan R wrote:
> Hi Christian,
> 
> On 6/10/2019 5:45 PM, Christian Lamparter wrote:
> > On Monday, June 10, 2019 12:09:56 PM CEST Sricharan R wrote:
> >> Hi Christian,
> >>
> >> On 6/6/2019 2:11 AM, Christian Lamparter wrote:
> >>> On Wed, Jun 5, 2019 at 7:16 PM Sricharan R <sricharan@codeaurora.org> wrote:
> >>>>
> >>>> Add initial device tree support for the Qualcomm IPQ6018 SoC and
> >>>> CP01 evaluation board.
> >>>>
> >>>> Signed-off-by: Sricharan R <sricharan@codeaurora.org>
> >>>> Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
> >>>> --- /dev/null
> >>>> +++ b/arch/arm64/boot/dts/qcom/ipq6018.dtsi
> >>>>
> >>>> +       clocks {
> >>>> +               sleep_clk: sleep_clk {
> >>>> +                       compatible = "fixed-clock";
> >>>> +                       clock-frequency = <32000>;
> >>>> +                       #clock-cells = <0>;
> >>>> +               };
> >>>> +
> >>> Recently-ish, we ran into an issue with the clock-frequency of the sleep_clk
> >>> on older IPQ40XX (and IPQ806x) on the OpenWrt Github and ML.
> >>> From what I know, the external "32KHz" crystals have 32768 Hz, but the QSDK
> >>> declares them at 32000 Hz. Since you probably have access to the BOM and
> >>> datasheets. Can you please confirm what's the real clock frequency for
> >>> the IPQ6018.
> >>> (And maybe also for the sleep_clk of the IPQ4018 as well?).
> >>>
> >>
> >> What exactly is the issue that you faced ?
> >> Looking in to the docs, it is <32000> only on ipq6018 and ipq40xx as well.
> > 
> > We need just a confirmation.
> > 
> > Then again, Currently the qcom-ipq4019.dtsi is using 32768 Hz.
> > 
> > |		sleep_clk: sleep_clk {
> > |			compatible = "fixed-clock";
> > |			clock-frequency = <32768>;
> > |			#clock-cells = <0>;
> > |		};
> > 
> > <https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/qcom-ipq4019.dtsi#L144>
> > 
> > Which makes sense, because all previous Qualcomm Atheros MIPS and the
> > future IPQ8072 SoCs have been either using or deriving a 32768 Hz clock.
> > 
> > For example: The AR9344 derives the clock from the 25MHz/40MHz external
> > oscillator. This is explained in "8.16.9 Derived RTC Clock (DERIVED_RTC_CLK)".
> > Which mentions that the "32KHz" clock interval is 30.5 usec / 30.48 usec
> > depending whenever the external reference crystal has 40MHz or 25MHz.
> > (1/30.5usec = 32.7868852 kilohertz!). The QCA9558 datasheet says the same
> > in "10.19.11 Derived RTC Clock". 
> > 
> > For IPQ8072: I point to the post by Sven Eckelmann on the OpenWrt ML:
> > <http://lists.infradead.org/pipermail/openwrt-devel/2019-May/017131.html>
> > "I was only able to verify for IPQ8072 that it had a 32.768 KHz
> > sleep clock." 
> > 
> > So this is pretty much "why there is an issue", it's confusing.
> > Is possible can you please look if there are (fixed) divisors values
> > listed in the documentation or the registers and bits that the values
> > are stored in? Because then we could just calculate it. 
> > 
> 
> Really sorry for the confusion. So looking little more, SLEEP_CLK is derived
> from an external 38.4MHZ crystal, it is 32.768 KHZ.
That's really valuable information to have. Thank you!

> Somehow the clk freq plan etc seems to mention them only as .032 MHZ and misses
> out. That means i will correct the patch for 32768 and probably the
> ipq8074.dtsi as well

Ok, there's one more issue that Paul found (at least with the IPQ4019),
https://patchwork.ozlabs.org/patch/1099482

it seems that the "sleep_clk" node in the qcom-ipq4019.dtsi is not used by
the gcc-ipq4019.c clk driver. this causes both wifi rtc_clks and the usb sleep
clks to dangle in the /sys/kernel/debug/clk/clk_summary (from a RT-AC58U)

   clock                         enable_cnt  prepare_cnt        rate   accuracy   phase
----------------------------------------------------------------------------------------
 xo                                       9            9    48000000          0 0
 [...]
 sleep_clk                                1            1       32768          0 0  
 gcc_wcss5g_rtc_clk                       1            1           0          0 0  
 gcc_wcss2g_rtc_clk                       1            1           0          0 0  
 gcc_usb3_sleep_clk                       1            1           0          0 0  
 gcc_usb2_sleep_clk                       1            1           0          0 0  

with his patch the /sys/kernel/debug/clk/clk_summary looks "better" 

(something like this:)

   clock                         enable_cnt  prepare_cnt        rate   accuracy   phase
----------------------------------------------------------------------------------------
 xo                                       9            9    48000000          0 0
 [...] 
 gcc_sleep_clk_src                        5            5       32000          0 0  
    gcc_wcss5g_rtc_clk                    1            1       32000          0 0  
    gcc_wcss2g_rtc_clk                    1            1       32000          0 0  
    gcc_usb3_sleep_clk                    1            1       32000          0 0  
    gcc_usb2_sleep_clk                    1            1       32000          0 0  

but judging from your comment "SLEEP_CLK is derived from an
external 38.4MHZ crystal" the gcc_sleep_clk_src / sleep_clk
should have xo as the parent. so the ideal output should be:

   clock                         enable_cnt  prepare_cnt        rate   accuracy   phase
----------------------------------------------------------------------------------------
 xo                                      10           10    48000000          0 0
 [...] 
    gcc_sleep_clk                         5            5       32768          0 0  
       gcc_wcss5g_rtc_clk                 1            1       32768          0 0  
       gcc_wcss2g_rtc_clk                 1            1       32768          0 0  
       gcc_usb3_sleep_clk                 1            1       32768          0 0  
       gcc_usb2_sleep_clk                 1            1       32768          0 0  

or am I missing/skipping over something important? 

Regards,
Christian




  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-05 17:15 [PATCH 0/6] Add minimal boot support for IPQ6018 Sricharan R
2019-06-05 17:15 ` [PATCH 1/6] pinctrl: qcom: Add ipq6018 pinctrl driver Sricharan R
2019-06-08  3:26   ` Bjorn Andersson
2019-06-10 11:00     ` Sricharan R
2019-06-05 17:15 ` [PATCH 2/6] dt-bindings: qcom: Add ipq6018 bindings Sricharan R
2019-06-08  3:27   ` Bjorn Andersson
2019-06-10 11:01     ` Sricharan R
2019-06-19 14:54   ` Rob Herring
2019-06-05 17:15 ` [PATCH 3/6] clk: qcom: Add DT bindings for ipq6018 gcc clock controller Sricharan R
2019-06-08  3:33   ` Bjorn Andersson
2019-06-05 17:16 ` [PATCH 5/6] arm64: dts: Add ipq6018 SoC and CP01 board support Sricharan R
2019-06-05 17:26   ` Marc Zyngier
2019-06-08  2:44     ` Sricharan R
2019-06-05 20:41   ` Christian Lamparter
2019-06-10 10:09     ` Sricharan R
2019-06-10 12:15       ` Christian Lamparter
2019-06-12  9:48         ` Sricharan R
2019-06-14 20:41           ` Christian Lamparter [this message]
2019-06-19 14:42             ` Sricharan R
2019-06-20 15:32               ` Christian Lamparter
2019-06-24 12:08                 ` Sricharan R
2019-06-08  3:48   ` Bjorn Andersson
2019-06-10 15:45     ` Sricharan R
2019-06-10 16:48       ` Stephen Boyd
2019-06-05 17:16 ` [PATCH 6/6] arm64: defconfig: Enable qcom ipq6018 clock and pinctrl Sricharan R
2019-06-08  3:32   ` Bjorn Andersson
2019-06-05 17:26 ` [PATCH 0/6] Add minimal boot support for IPQ6018 Sricharan R
2019-06-07 23:08 ` Linus Walleij
     [not found] ` <1559754961-26783-5-git-send-email-sricharan@codeaurora.org>
2019-06-08  3:32   ` [PATCH 4/6] clk: qcom: Add ipq6018 Global Clock Controller support Bjorn Andersson
2019-06-10 11:47     ` Sricharan R
2019-06-10 16:58       ` Bjorn Andersson
2019-06-05 17:28 [PATCH 0/6] Add minimal boot support for IPQ6018 Sricharan R
2019-06-05 17:28 ` [PATCH 5/6] arm64: dts: Add ipq6018 SoC and CP01 board support Sricharan R
2019-06-05 17:34   ` Sudeep Holla
2019-06-08  2:44     ` Sricharan R

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