linux-kernel - Re: [PATCH V10 4/9] mfd: pm8008: Add reset-gpios

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Message-ID: <CAE-0n532pgMKBFmK2etwCjMydKqD276X-veqqsne=WgE-sUegA@mail.gmail.com>
Date:   Tue, 26 Apr 2022 23:30:07 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Satya Priya Kakitapalli <quic_c_skakit@...cinc.com>
Cc:     linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V10 4/9] mfd: pm8008: Add reset-gpios

Quoting Satya Priya Kakitapalli (Temp) (2022-04-26 23:03:08)
>
> On 4/27/2022 10:58 AM, Satya Priya Kakitapalli (Temp) wrote:
> >
> > On 4/18/2022 10:34 AM, Satya Priya Kakitapalli (Temp) wrote:
> >>
> >> On 4/15/2022 5:40 AM, Stephen Boyd wrote:
> >>> Quoting Satya Priya (2022-04-14 05:30:13)
> >>>> diff --git a/drivers/mfd/qcom-pm8008.c b/drivers/mfd/qcom-pm8008.c
> >>>> index c472d7f..97a72da 100644
> >>>> --- a/drivers/mfd/qcom-pm8008.c
> >>>> +++ b/drivers/mfd/qcom-pm8008.c
> >>
> >>>> +               return PTR_ERR(chip->reset_gpio);
> >>>> +       }
> >>>> +       gpiod_set_value(chip->reset_gpio, 1);
> >>> Does this do anything? Does this work just as well?
> >>>
> >>>     reset_gpio = devm_gpiod_get(chip->dev, "reset", GPIOD_OUT_LOW);
> >>>     if (IS_ERR(reset_gpio))
> >>>         return PTR_ERR(reset_gpio);
> >>>
> >
> > This is not working as expected. We need to add
> > "gpiod_set_value(chip->reset_gpio, 1);"  to actually toggle the line.
> >
>
> I checked again and it is working after using GPIOD_OUT_HIGH instead of LOW.
>
> reset_gpio = devm_gpiod_get(chip->dev, "reset", GPIOD_OUT_HIGH);
>      if (IS_ERR(reset_gpio))
>          return PTR_ERR(reset_gpio);
>

What do you have in DT for the 'reset-gpios' property? GPIOD_OUT_HIGH
means the reset line is asserted, which presumably you don't want to be
the case because you typically deassert a reset to "take it out of
reset". Using GPIOD_OUT_HIGH probably works because DT has the wrong
GPIO flag, i.e.  GPIO_ACTIVE_HIGH, for an active low reset, or vice
versa.