linux-kernel - Re: gpio: gpio-pci-idio-16 regression after LTS upgrade

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Message-ID: <jajbilboyqty3a5tbgjgwklrpcstv7gotkqis46cuzgew7ip4q@ej37jq2cev77>
Date: Tue, 14 Oct 2025 14:21:18 +0300
From: Ioana Ciornei <ioana.ciornei@....com>
To: Michael Walle <mwalle@...nel.org>
Cc: William Breathitt Gray <wbg@...nel.org>, 
	Mark Cave-Ayland <mark.caveayland@...anix.com>, linus.walleij@...aro.org, brgl@...ev.pl, 
	andriy.shevchenko@...ux.intel.com, broonie@...nel.org, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: gpio: gpio-pci-idio-16 regression after LTS upgrade

On Tue, Oct 14, 2025 at 11:03:25AM +0200, Michael Walle wrote:
> Hi,
> 
> On Thu Oct 9, 2025 at 11:49 AM CEST, William Breathitt Gray wrote:
> > On Thu, Oct 09, 2025 at 10:05:58AM +0100, Mark Cave-Ayland wrote:
> >> On 07/10/2025 09:16, William Breathitt Gray wrote:
> >> > So the intention I had with gpio-idio-16 was to provide reg_dat_base and
> >> > reg_set_base to define the input and output bases, and then
> >> > reg_mask_xlate would do the translation between input and outputs. I
> >> > think this design is allowed by gpio-regmap, is it not Michael?
> >> >
> >> > In theory, gpio_regmap_get_direction should call gpio->reg_mask_xlate()
> >> > which is mapped to idio_16_reg_mask_xlate(), and thus set reg and mask
> >> > which then is evaluated at the end of gpio_regmap_get_direction() to
> >> > determine which direction to return.
> >> >
> >> > Is it possible idio_16_reg_mask_xlate() is returning the wrong values
> >> > for reg and mask?
> >> >
> >> > William Breathitt Gray
> >> 
> >> The only logic around .reg_dat_base and .reg_set_base in
> >> gpio_regmap_get_direction() is this:
> >> 
> >> 	if (gpio->reg_dat_base && !gpio->reg_set_base)
> >> 		return GPIO_LINE_DIRECTION_IN;
> >> 	if (gpio->reg_set_base && !gpio->reg_dat_base)
> >> 		return GPIO_LINE_DIRECTION_OUT;
> >> 
> >> Otherwise it attempts to use .reg_dir_out_base and .reg_dir_in_base
> >> which are not set for gpio-idio-16 because the GPIO directions are fixed
> >> and not controlled via a data-direction register. And as these are not
> >> set, gpio_regmap_get_direction() returns -ENOTSUPP.
> >> 
> >> Were you thinking that gpio_regmap_get_direction() should have some
> >> additional direction logic if both .reg_dat_base and .reg_set_base are
> >> set, based upon their comparative values?
> >
> > Ah you're right, I misunderstood the logic in gpio_regmap_get_direction.
> > So essentially the problem is that gpio-idio-16 has no way of indicating
> > the direction of its I/O because it's mixed.
> >
> > The IDIO-16 series lacks a direction setting register, so I think the
> > proper solution is as you suggest: add support for a get_direction
> > callback to struct gpio_regmap_config in the same vein as the existing
> > reg_mask_xlate callback. Then in gpio_regmap_register you can set
> > gpio->get_direction = config->get_direction in the same way
> > config->reg_mask_xlate is handled.
> 
> IIUC the chip has fixed input and outputs. In that case this should
> help:
> https://lore.kernel.org/all/20250922142427.3310221-8-ioana.ciornei@nxp.com/
> 
> I guess Ioana will resubmit the series for this cycle.

Yes, I will resubmit shortly.

> To fix the regression, I guess the patch can then be picked up by the
> stable team along with the driver patch which will set the
> .fixed_direction_output config field.

Just to make sure that I understand, do you want me to add another patch
that adds the new driver user or that will be handled separately?

Ioana