linux-kernel - Re: [PATCH v3 4/5] PCI: imx6: Convert to agnostic GPIO API

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Date: Tue, 7 May 2024 12:00:10 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Frank Li <Frank.Li@....com>, 
	Krzysztof Wilczyński <kwilczynski@...nel.org>, 
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, 
	linux-omap@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	imx@...ts.linux.dev, linux-amlogic@...ts.infradead.org, 
	linux-arm-msm@...r.kernel.org, linux-tegra@...r.kernel.org, 
	Vignesh Raghavendra <vigneshr@...com>, Siddharth Vadapalli <s-vadapalli@...com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Richard Zhu <hongxing.zhu@....com>, Lucas Stach <l.stach@...gutronix.de>, 
	Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, 
	Yue Wang <yue.wang@...ogic.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Kevin Hilman <khilman@...libre.com>, Jerome Brunet <jbrunet@...libre.com>, 
	Martin Blumenstingl <martin.blumenstingl@...glemail.com>, 
	Xiaowei Song <songxiaowei@...ilicon.com>, Binghui Wang <wangbinghui@...ilicon.com>, 
	Thierry Reding <thierry.reding@...il.com>, Jonathan Hunter <jonathanh@...dia.com>, 
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>, Pali Rohár <pali@...nel.org>
Subject: Re: [PATCH v3 4/5] PCI: imx6: Convert to agnostic GPIO API

On Tue, May 7, 2024 at 10:28 AM Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> On Tue, May 07, 2024 at 01:44:56PM +0530, Manivannan Sadhasivam wrote:
> > On Mon, May 06, 2024 at 02:10:24PM +0200, Linus Walleij wrote:
> > > On Mon, Apr 29, 2024 at 12:25 PM Andy Shevchenko
> > > <andriy.shevchenko@...ux.intel.com> wrote:
> > >
> > > > The of_gpio.h is going to be removed. In preparation of that convert
> > > > the driver to the agnostic API.
> > > >
> > > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > > Reviewed-by: Frank Li <Frank.Li@....com>
> > > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > >
> > > I think there is a bug here, the code is respecting the OF property
> > > "reset-gpio-active-high"
> > > but the code in drivers/gpio/gpiolib-of.h actually has a quirk for
> > > this so you can just
> > > delete all the active high handling and rely on 1 = asserted and 0 =
> > > deasserted when
> > > using GPIO descriptors.
> > >
> >
> > Wow...
> >
> > So this bug is present even before this series, right?
> >
> > > Just delete this thing:
> > > imx6_pcie->gpio_active_high = of_property_read_bool(node,
> > >                                            "reset-gpio-active-high");
> >
> > But this is just a bandaid IMO. The flag for the PERST# GPIO should be properly
> > set in the board dts as per the board design.
> >
>
> Hmm, no. I was confused by the property. But this quirk in gpiolib-of.c is going
> to be applied while changing the GPIO state also or just during request time?

It's applied permanentlt at request and then the descriptors maintain their
polarity state over the course of their lifetime.

Yours,
Linus Walleij