linux-kernel - Re: [PATCH V1] pinctrl: qcom: spmi-gpio: Update GPIO EN

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Date:   Sun, 8 Oct 2017 22:56:43 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Fenglin Wu <fenglinw@...eaurora.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, collinsd@...eaurora.org,
        aghayal@...eaurora.org, wruan@...eaurora.org,
        subbaram@...eaurora.org, kgunda@...eaurora.org
Subject: Re: [PATCH V1] pinctrl: qcom: spmi-gpio: Update GPIO EN_CTL when
 setting pin config

On Sun 08 Oct 22:34 PDT 2017, Fenglin Wu wrote:

> On 10/6/2017 12:27 AM, Bjorn Andersson wrote:
> > On Mon 11 Sep 17:32 PDT 2017, fenglinw@...eaurora.org wrote:
> > 
> > > From: Fenglin Wu <fenglinw@...eaurora.org>
> > > 
> > > GPIO is expected to be disabled iff PIN_CONFIG_BIAS_HIGH_IMPEDANCE is
> > > configured. Update is_enabled flag in config_set() so that it can
> > > reflect GPIO status correctly. Also modify EN_CTL register based on
> > > is_enabled flag in config_set() to configure the GPIO properly.
> > > 
> > > Signed-off-by: Fenglin Wu <fenglinw@...eaurora.org>
> > > ---
> > >   drivers/pinctrl/qcom/pinctrl-spmi-gpio.c | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
> > > index c2c0bab..a0edaa8 100644
> > > --- a/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
> > > +++ b/drivers/pinctrl/qcom/pinctrl-spmi-gpio.c
> > > @@ -453,6 +453,7 @@ static int pmic_gpio_config_set(struct pinctrl_dev *pctldev, unsigned int pin,
> > >   	pad = pctldev->desc->pins[pin].drv_data;
> > > +	pad->is_enabled = true;
> > >   	for (i = 0; i < nconfs; i++) {
> > >   		param = pinconf_to_config_param(configs[i]);
> > >   		arg = pinconf_to_config_argument(configs[i]);
> > > @@ -600,6 +601,10 @@ static int pmic_gpio_config_set(struct pinctrl_dev *pctldev, unsigned int pin,
> > >   			return ret;
> > >   	}
> > > +	val = pad->is_enabled << PMIC_GPIO_REG_MASTER_EN_SHIFT;
> > > +
> > > +	ret = pmic_gpio_write(state, pad, PMIC_GPIO_REG_EN_CTL, val);
> > > +
> > 
> > This looks good.
> > 
> > Acked-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> > 
> > 
> > But I spotted another issue while reviewing this; currently the initial
> > state of is_enabled is unconditionally set to enabled in
> > pmic_gpio_populate(), so reading the initial pinconf or configuring a
> > pinmux before setting a pinconf will operate on the potentially wrong
> > information.
> > 
> > So I think the initial value should be read out from REG_EN_CTL rather
> > than being just "true".
> > 
> > Can you please either submit another patch for this?
> 
> Hmm, considering a GPIO which is disabled by default in hardware
> setting, what's its expected state if we only define "function" for it?
> I was thinking we need to enable it once it has any setting in pinmux or
> pinconf. If you think that we need to keep its original state until we
> set pinconf for it, yes, I can submit a change to address this.
> 

Are there valid cases where only function should be selected and no
other configuration is used? If so it makes sense to make
pmic_gpio_set_mux() enable the block.


Regardless of this, if there are disabled pins that are not mentioned in
DT they will still appear as enabled in the debugfs interface; and this
I consider an error worth fixing.

Regards,
Bjorn