linux-kernel - Re: [PATCH v6 2/3] pinctrl: qcom: add support for complementary reserved gpios

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Date:   Mon,  3 Oct 2022 20:52:33 -0400
From:   Richard Acayan <mailingradian@...il.com>
To:     linux-arm-msm@...r.kernel.org
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Richard Acayan <mailingradian@...il.com>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v6 2/3] pinctrl: qcom: add support for complementary reserved gpios

> On Sat, Oct 01, 2022 at 05:07:24PM -0400, Richard Acayan wrote:
> > The driver-provided list of reserved gpios normally overrides any valid
> > ranges provided by the firmware (device tree and ACPI). When the driver
> > defines dummy pingroups by itself, it should mark these as invalid but
> > should not prevent the firmware from specifying more reserved gpios. Let
> > pinctrl drivers indicate that the reserved gpios list complements instead
> > of overrides other lists from firmware.
> > 
> > Signed-off-by: Richard Acayan <mailingradian@...il.com>
> > ---
> >  drivers/pinctrl/qcom/pinctrl-msm.c | 5 +++--
> >  drivers/pinctrl/qcom/pinctrl-msm.h | 4 ++++
> >  2 files changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pinctrl/qcom/pinctrl-msm.c b/drivers/pinctrl/qcom/pinctrl-msm.c
> > index a2abfe987ab1..cea1d2af8c88 100644
> > --- a/drivers/pinctrl/qcom/pinctrl-msm.c
> > +++ b/drivers/pinctrl/qcom/pinctrl-msm.c
> > @@ -687,9 +687,10 @@ static int msm_gpio_init_valid_mask(struct gpio_chip *gc,
> >  	const int *reserved = pctrl->soc->reserved_gpios;
> >  	u16 *tmp;
> >  
> > -	/* Driver provided reserved list overrides DT and ACPI */
> > +	/* Driver provided reserved list overrides DT and ACPI by default */
> >  	if (reserved) {
> > -		bitmap_fill(valid_mask, ngpios);
> > +		if (!pctrl->soc->complement_fw_gpio_ranges)
> 
> reserved_gpios is only defined for ACPI drivers and afaict there's
> nothing in the ACPI path that would modify the valid_mask after the
> bitmap is being filled in gpiochip_allocate_mask().
> 
> If that's the case it seems reasonable that we can just drop the
> bitmap_fill() here. But perhaps I'm missing something?

This was me trying to be as uninvasive to existing drivers as I could.
I just assumed that it was important because it was there already and
the comment suggested that it was what the original developer wanted.

When looking at it a bit closer, the bitmap_fill() call in
gpiochip_alloc_valid_mask() wasn't present at the original commit that
added this line. I'm guessing this means it's safe to remove, but just
in case (for the next version):

Cc: Lee Jones <lee@...nel.org>

> 
> Regards,
> Bjorn
> 
> > +			bitmap_fill(valid_mask, ngpios);
> >  		for (i = 0; reserved[i] >= 0; i++) {
> >  			if (i >= ngpios || reserved[i] >= ngpios) {
> >  				dev_err(pctrl->dev, "invalid list of reserved GPIOs\n");
> > diff --git a/drivers/pinctrl/qcom/pinctrl-msm.h b/drivers/pinctrl/qcom/pinctrl-msm.h
> > index dd0d949f7a9e..734fe7b2a472 100644
> > --- a/drivers/pinctrl/qcom/pinctrl-msm.h
> > +++ b/drivers/pinctrl/qcom/pinctrl-msm.h
> > @@ -128,6 +128,9 @@ struct msm_gpio_wakeirq_map {
> >   *              function number for eGPIO and any time we see that function
> >   *              number used we'll treat it as a request to mux away from
> >   *              our TLMM towards another owner.
> > + * @complement_fw_gpio_ranges: If true, the reserved gpios list from the
> > + *                             driver will not override the reserved gpios
> > + *                             list from the firmware.
> >   */
> >  struct msm_pinctrl_soc_data {
> >  	const struct pinctrl_pin_desc *pins;
> > @@ -146,6 +149,7 @@ struct msm_pinctrl_soc_data {
> >  	bool wakeirq_dual_edge_errata;
> >  	unsigned int gpio_func;
> >  	unsigned int egpio_func;
> > +	bool complement_fw_gpio_ranges;
> >  };
> >  
> >  extern const struct dev_pm_ops msm_pinctrl_dev_pm_ops;
> > -- 
> > 2.37.3
> >