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Date:   Tue, 26 Mar 2019 11:58:05 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Anand Moon <linux.amoon@...il.com>
Cc:     devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Subject: Re: [PATCH v1] ARM: dts: exynos: Add proper regulator states for
 suspend-to-mem for odroid-u3

On Tue, 26 Mar 2019 at 11:35, Anand Moon <linux.amoon@...il.com> wrote:

(...)

> > This is third or fourth submission but you marked it as v1. This makes
> > it very difficult to discuss and reference previous versions.
> >
> > The commit message did not change since beginning (first version). I
> > asked twice that you need to explain exactly why you put the the
> > regulator to off or on state in suspend. Why?
> > Because:
> > 1. This change looks without justification - once you put on, then you
> > put off, now again on,
> > 2. Anyone reading the code later must know the rationale why this was done,
> > 3. I am not quite sure whether this is good setting so I would be
> > happy to be convinced.
> >
>
> Like I mention in the patch summary that this.
>
> Current changes are based on
> [0] https://www.kernel.org/doc/Documentation/devicetree/bindings/regulator/max77686.txt
>
>   Regulators which can be turned off during system suspend:
> -LDOn : 2, 6-8, 10-12, 14-16,
> -BUCKn : 1-4.
>   Use standard regulator bindings for it ('regulator-off-in-suspend').

I do not see how this is related to my questions.

> > How to provide such explanation? The best in commit message. Sometimes
> > in the comment in the code, depends.
>
> Ok I have been testing with following regulator debug prints to catch error.
> [0] max77686-regulator.patch
>
> below is the console logs during suspend and resume.
> -------------------------------------------------------------------------------
> Last login: Sat Mar 23 18:22:46 on ttySAC1
> [root@...hl-u3e ~]# echo no > /sys/module/printk/parameters/console_suspend
> [root@...hl-u3e ~]# rtcwake -d /dev/rtc0 -m mem -s 10
> rtcwake: wakeup from "mem" using /dev/rtc0 at Sat Mar 23 19:56:17 2019
> [   38.595854] PM: suspend entry (deep)
> [   38.596603] PM: Syncing filesystems ... done.
> [   38.629351] Freezing user space processes ... (elapsed 0.002 seconds) done.
> [   38.633192] OOM killer disabled.
> [   38.636035] Freezing remaining freezable tasks ... (elapsed 0.001
> seconds) done.
> [   38.675059] smsc95xx 1-2:1.0 eth0: entering SUSPEND2 mode
> [   38.753120] dwc2 12480000.hsotg: suspending usb gadget g_ether
> [   38.754007] dwc2 12480000.hsotg: new device is full-speed
> [   38.758960] dwc2 12480000.hsotg: dwc2_hsotg_ep_disable: called for ep0
> [   38.765507] dwc2 12480000.hsotg: dwc2_hsotg_ep_disable: called for ep0
> [   38.774050] wake enabled for irq 119
> [   38.775761] BUCK9: No configuration
> [   38.779191] BUCK8_P3V3: No configuration
> [   38.782852] BUCK7_2.0V: No configuration
> [   38.786851] BUCK6_1.35V: No configuration
> [   38.790752] VDDQ_CKEM1_2_1.2V: No configuration
> [   38.796220] BUCK4: regulator suspend disable supported
> [   38.800769] BUCK3: regulator suspend disable supported
> [   38.806002] BUCK1: regulator suspend disable supported
> [   38.810644] LDO26: No configuration
> [   38.814169] VDDQ_LCD_1.8V: No configuration
> [   38.818267] LDO24: No configuration
> [   38.821732] LDO23: No configuration
> [   38.825262] LDO22_VDDQ_MMC4_2.8V: No configuration
> [   38.829992] TFLASH_2.8V: No configuration
> [   38.834040] LDO20_1.8V: No configuration
> [   38.837883] LDO19: No configuration
> [   38.841349] LDO18: No configuration
> [   38.844878] LDO17: No configuration
> [   38.848667] LDO16: regulator suspend disable supported
> [   38.853889] LDO15: regulator suspend disable supported
> [   38.858931] LDO14: regulator suspend disable supported
> [   38.863771] VDDQ_C2C_W_1.8V: No configuration
> [   38.868378] LDO12: regulator suspend disable supported
> [   38.873508] LDO11: regulator suspend disable supported
> [   38.878545] LDO10: regulator suspend disable supported
> [   38.883384] LDO9: No configuration
> [   38.887190] LDO8: regulator suspend disable supported
> [   38.892168] LDO7: regulator suspend disable supported
> [   38.897279] LDO6: regulator suspend disable supported
> [   38.901872] VDDQ_MMC1_3_1.8V: No configuration
> [   38.906363] VDDQ_MMC2_2.8V: No configuration
> [   38.910541] VDDQ_EXT_1.8V: No configuration
> [   38.915134] LDO2: regulator suspend disable supported
> [   38.919753] VDD_ALIVE_1.0V: No configuration
> [   38.935229] usb3503 0-0008: switched to STANDBY mode
> [   38.935981] wake enabled for irq 123
> [   38.955192] samsung-pinctrl 11000000.pinctrl: Setting external
> wakeup interrupt mask: 0xfbfff7ff
> [   38.975448] Disabling non-boot CPUs ...
> [   39.029279] s3c2410-wdt 10060000.watchdog: watchdog disabled
> [   39.029576] wake disabled for irq 123
> [   39.044319] usb3503 0-0008: switched to HUB mode
> [   39.144089] wake disabled for irq 119
> [   39.144812] dwc2 12480000.hsotg: resuming usb gadget g_ether
> [   39.422626] usb 1-2: reset high-speed USB device number 2 using exynos-ehci
> [   39.774632] usb 1-3: reset high-speed USB device number 3 using exynos-ehci
> [   40.106478] OOM killer enabled.
> [   40.106609] Restarting tasks ... done.
> [   40.111100] PM: suspend exit
> [   40.124058] mmc_host mmc1: Bus speed (slot 0) = 50000000Hz (slot
> req 400000Hz, actual 396825HZ div = 63)
> [root@...hl-u3e ~]# [   40.364705] mmc_host mmc1: Bus speed (slot 0) =
> 50000000Hz (slot req 52000000Hz, actual 50000000HZ div = 0)
> [   41.220200] smsc95xx 1-2:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0xC5E1
> -------------------------------------------------------------------------------
> > How such explanation could look like? For example like this:
> > f8f3b7fc21b1 ("ARM: dts: exynos: Fix regulators configuration on Peach
> > Pi/Pit Chromebooks")
> > Marek clearly explained why he put the regulators "always-on", even
> > tough we do not know everything about this. More over, he mentions
> > that this fixes specific issue.
> >
>
> Thanks but I am not the expert here in general with regulator on/off.
> I will add comment if needed explain in more detail.

This kernel log does not prove whether these DTS properties make sense
or whether are proper at all. They  prove that kernel uses some
configuration but I did not ask for this.

>
> [snip]
>
> > Summarizing, please answer:
> > 1. Why this is made off-in-suspend?
> > 2. Why this can be made off-in-suspend?
> >
>
> On MAX77686A PMIC. (some quote from the datasheet).
>
> Power ON/OFF by PWRREQ in PMIC=ON sequence is only effective when ON/OFF
> on all regulators above are assigned by PWRREQ=H/L.
>
> All programming must be done before the AP enters the sleep mode by
> pulling PWRREQ low since
> the AP does not have programming capability in (deep) sleep mode.
>
> *Regulator are not really turned off but set into IDLE  / Standby
> state too be restored to Normal state*
>
> Power summary in image : [1] https://imgur.com/gallery/l74kliX
>
> Power Summary for MAX77686A of the regulator support PWRREQ
> Power   Default ON  |  ON/OFF
> --------------------------------------
> BUCK1  |  ON        | PWRREQ or I2C
> BUCK2  |  ON        | PWRREQ or I2C
> BUCK3  |  ON        | PWRREQ or I2C
> BUCK4  |  ON        | PWREWQ or I2C
> BUCK5  |  ON        | I2C
> BUCK6  |  ON        | I2C
> BUCK7  |  ON        | I2C
> BUCK8  |  OFF       | I2C or ENB8 The external enable/disable pin, ENB8
> BUCK9  |  OFF       | I2C or ENB9 The external enable/disable pin, ENB9
> LDO1   |  ON        | I2C
> LDO2   |  ON        | PWRREQ or I2C
> LDO3   |  ON        | I2C
> LDO4   |  ON        | I2C
> LDO5   |  ON        | I2C
> LDO6   |  ON        | PWRREQ or I2C
> LDO7   |  ON        | PWRREQ or I2C
> LDO8   |  ON        | PWRREQ or I2C
> LDO9   |  OFF       | I2C
> LDO10  |  ON        | PWRREQ or I2C
> LDO11  |  ON        | PWRREQ or I2C
> LDO12  |  ON        | PWRREQ or I2C
> LDO13  |  ON        | I2C
> LDO14  |  ON        | PWRREQ or I2C
> LDO15  |  ON        | PWRREQ or I2C
> LDO16  |  ON        | PWRREQ or I2C
> LDO17  |  OFF       | I2C
> LDO18  |  OFF       | I2C
> LDO19  |  OFF       | I2C
> LDO20  |  OFF       | I2C OR ENL20 ENL20, external enable/disable pin
> LDO21  |  OFF       | I2C OR ENL21 ENL21, external enable/disable pin
> LDO22  |  OFF       | I2C OR ENL22 ENL22, external enable/disable pin
> LDO23  |  OFF       | I2C
> LDO24  |  OFF       | I2C
> LDO25  |  OFF       | I2C
> LDO26  |  OFF       | I2C

You quoted the datasheet which describes PMIC behavior. This does not
answer to my two questions at all.

>
> > >                         ldo20_reg: LDO20 {
> > > @@ -421,6 +451,9 @@
> > >                                 regulator-max-microvolt = <1100000>;
> > >                                 regulator-always-on;
> > >                                 regulator-boot-on;
> > > +                               regulator-state-mem {
> > > +                                       regulator-off-in-suspend;
> > > +                               };
> > >                         };
> >
> > I questioned this change two times. You did not answer to my
> > question... If you turn memory bus regulator off, how the memory will
> > work in Suspend-to-Memory mode? I might be missing here something but
> > it just looks suspicious. Maybe the regulator does not supply the
> > memory itself (so refresh works even when it is down), just the
> > interface? I don't know, it just looks suspicious. I need to see
> > proper explanation.
> >
> > I am sorry but I will not check other hunks in this patch. Please
> > provide the answers for all my questions here first.
> >
>
> As per above table of MAX77686 PWRREQ capabilities regulator nodes
> can be turned off during suspend reset of them remain on during suspend.

Just because something can be turned off does not mean that it should.
Apparently you made this assumption everywhere here and for my
questions "why?" you reply "datasheet of PMIC says it can be done".
This is wrong assumption and wrong justification for the patch.

I cannot accept this. Please answer my questions and provide proper
rationale for this patch.

>
> > Best regards,
> > Krzysztof
> >
>
> We could monitor the regulator states via sys filesystem and also
> using below tool
> https://git.linaro.org/power/powerdebug.git
>
> I have tried to summaries the feature required for this patch.
> some of which I have overlooked earlier before sending the patch.
>
> I am really poor in english for transform / interpreter the technical details
> required at for your queries. But I will try to improve my self in the future.

Again this is observing of kernel behavior after applying patch. It
has nothing to do whether change should be implemented and how it
affects real hardware. This is not even a measurement...

Best regards,
Krzysztof

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