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From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Thu, 15 Jul 2021 01:30:23 +0200
Message-ID: <CAFBinCBtZDRH_xTn3hUBbAPNGrut2cbEQOSuEN1vwObP1Ns5qw@mail.gmail.com>
Subject: Re: [PATCHv1 1/3] ARM: dts: meson8b: odroidc1: Add usb phy power node
To:     Anand Moon <linux.amoon@gmail.com>
Cc:     linux-phy@lists.infradead.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-amlogic@lists.infradead.org,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Matt Corallo <oc2udbzfd@mattcorallo.com>,
        Rob Herring <robh+dt@kernel.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Vinod Koul <vkoul@kernel.org>,
        Emiliano Ingrassia <ingrassia@epigenesys.com>,
        devicetree <devicetree@vger.kernel.org>
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Hi Anand,

On Wed, Jul 14, 2021 at 7:25 PM Anand Moon <linux.amoon@gmail.com> wrote:
[...]
> Can you give these small changes a try,
> $ git diff
> diff --git a/arch/arm/boot/dts/meson8b-odroidc1.dts
> b/arch/arm/boot/dts/meson8b-odroidc1.dts
> index 748f4c6a050a..066523f14074 100644
> --- a/arch/arm/boot/dts/meson8b-odroidc1.dts
> +++ b/arch/arm/boot/dts/meson8b-odroidc1.dts
> @@ -47,8 +47,9 @@ usb_pwr_en: regulator-usb-pwr-en {
>                 /*
>                  * signal name from schematics: PWREN
>                  */
> -               gpio = <&gpio_ao GPIOAO_5 GPIO_ACTIVE_HIGH>;
> +               gpio = <&gpio_ao GPIOAO_5 GPIO_OPEN_DRAIN>;
>                 enable-active-high;
> +               regulator-always-on;
>         };
>
> [alarm@archl-c1e ~]$ sudo cat /sys/kernel/debug/gpio | grep usb
>  gpio-1953 (USB_HUB_RST_N       |usb-hub-reset       ) out hi
>  gpio-1954 (USB_OTG_PWREN       |regulator-usb-pwr-en) out lo
I can reproduce the /sys/kernel/debug/gpio output with this patch

Still USB works for me regardless of whether USB_OTG_PWREN is HIGH or LOW
This is something that is not possible if the regulator is really
connected on the board like you are describing in this patch.
If this .dts change was correct then I would expect that USB is
breaking when inverting the GPIO polarity.

I am using the "inverted GPIO polarity" approach to find the Ethernet
PHY reset GPIO when working on boards for which I don't have the
schematics:
1) make an assumption of which GPIO to use
2) try with GPIO_ACTIVE_LOW -> PHY should be detected
3) change it to GPIO_ACTIVE_HIGH -> PHY should not be found anymore
(because it's in reset)
4) before submitting the board.dts upstream I of course change it back
to GPIO_ACTIVE_LOW

If during step 3) the PHY is still found then I know that it's not the
correct GPIO.
I am seeing the same behavior with this USB regulator. My
interpretation of this is: either you are not using the right GPIO or
the GPIO is not related to &usb1 (or it's PHY).


Best regards,
Martin