linux-kernel - Re: [PATCH 3/3] PCI: qcom: Treat PHY and PERST# as optional for the new binding

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Message-ID: <CAMRc=Mf++D-jbEPmPKc1uAxeH_RZ==B1ybWy7oTWFwJ+kAcHyA@mail.gmail.com>
Date: Mon, 13 Oct 2025 11:43:06 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, linus.walleij@...aro.org, 
	Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Lorenzo Pieralisi <lpieralisi@...nel.org>, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Abraham I <kishon@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>, linux-pci@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Subject: Re: [PATCH 3/3] PCI: qcom: Treat PHY and PERST# as optional for the
 new binding

On Sat, Oct 11, 2025 at 6:09 AM Manivannan Sadhasivam <mani@...nel.org> wrote:
>
> + GPIO folks for the below API query
>
> On Fri, Oct 10, 2025 at 08:32:51PM +0200, Konrad Dybcio wrote:
> > On 10/10/25 8:25 PM, Manivannan Sadhasivam wrote:
> > > Even for the new DT binding where the PHY and PERST# properties are
> > > specified in the Root Port, both are optional. Hence, treat them as
> > > optional in the driver too.
> >
> > I suppose this makes sense if the PHY is transparent to the OS
> > or otherwise pre-programmed and PERST# is hardwired or otherwise
> > unnecessary.. both of which I suppose aren't totally impossible..
> >
>
> PERST# is by definition an optional signal, but I'm not sure about why PHY is
> not used by the controller driver.
>
> > >
> > > If both properties are not specified, then fall back to parsing the legacy
> > > binding for backwards compatibility.
> > >
> > > Fixes: a2fbecdbbb9d ("PCI: qcom: Add support for parsing the new Root Port binding")
> > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-qcom.c | 11 +++++++++--
> > >  1 file changed, 9 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 805edbbfe7eba496bc99ca82051dee43d240f359..d380981cf3ad78f549de3dc06bd2f626f8f53920 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -1720,13 +1720,20 @@ static int qcom_pcie_parse_port(struct qcom_pcie *pcie, struct device_node *node
> > >
> > >     reset = devm_fwnode_gpiod_get(dev, of_fwnode_handle(node),
> > >                                   "reset", GPIOD_OUT_HIGH, "PERST#");
> > > -   if (IS_ERR(reset))
> > > +   if (IS_ERR(reset) && PTR_ERR(reset) != -ENOENT)
> > >             return PTR_ERR(reset);
> >
> > Please introduce an _optional variant instead
> >
>
> Linus, Bartosz, are you OK with devm_fwnode_gpiod_get_optional() API? Just
> wanted to confirm before I go ahead as there are existing users checking for
> -ENOENT explicitly. Not sure if they are doing it for a reason other than the
> absence of the _optional variant or not.
>

I'm fine as long as it follows the conventions established by other
GPIOLIB _optional interfaces.

Bart