[PATCH 0/2] gpio: mmio: read the line direction from pinctrl on chips without direction registers

[Mehmet Fide]

From: Mehmet Fide <mehmet.fide at screeningeagle.com>

Hi Bartosz, Linus,

this is the series that replaces the gpiolib guard patch [1], along the
lines Bartosz suggested there: instead of teaching gpiod_get_direction()
to stay quiet when a chip has no get_direction(), give gpio-mmio one that
asks the pinctrl backend, and teach the pin controller to answer.

The user is the Vybrid GPIO block (gpio-vf610, a generic mmio chip with
GPIO_GENERIC_PINCTRL_BACKEND and no direction registers, the direction
lives in the iomuxc pad as the OBE bit). Today every
gpiod_get_direction() there trips the WARN in gpiolib, 21 backtraces per
boot on a Colibri VF61/VF50.

Patch 1 is the pinctrl-imx side. Bartosz asked whether the raw register
coming back from pin_config_get() is a bug in pinctrl-imx: it is, the
callback never looked at which parameter was requested. This patch makes
it parameter aware for PIN_CONFIG_OUTPUT_ENABLE and
PIN_CONFIG_INPUT_ENABLE on SoCs that say where those bits live (Vybrid:
OBE bit 1, IBE bit 0), and keeps the raw register as the fallback for
everything else, because the debugfs dump still relies on it. Converting
the driver fully to generic pinconf is a bigger job than this fix needs.

Patch 2 installs the get_direction() callback in gpio-mmio for the
"pinctrl backend, no direction registers" combination, mirroring how the
direction setters are already forwarded.

Tested on a Colibri VF61 (Iris carrier) on top of gpio/for-next: the 21
boot-time backtraces are gone, and /sys/kernel/debug/gpio now shows the
pad's real direction for every requested line (the hogs, the SD card
detect input, the USB VBUS regulator output). Pads with no pinctrl
configuration in the device tree cannot be queried and report -ENOTSUPP;
those pads cannot change direction through this chip either, as the
existing direction setters return -EINVAL for them, so nothing that
worked before is affected.

Patch 2 needs patch 1 to give correct answers: with the raw register
coming back, the direction would be read from the wrong bits. Taking
both through one tree, with an ack from the other side, avoids that
window.

[1] https://lore.kernel.org/linux-gpio/20260813193715.2346477-1-mehmet.fide@gmail.com/

Mehmet Fide (2):
  pinctrl: imx: answer OUTPUT_ENABLE/INPUT_ENABLE queries from the pad
    register
  gpio: mmio: get the direction from pinctrl when there are no direction
    registers

 drivers/gpio/gpio-mmio.c                  | 27 ++++++++++++++++++++
 drivers/pinctrl/freescale/pinctrl-imx.c   | 30 +++++++++++++++++++++++
 drivers/pinctrl/freescale/pinctrl-imx.h   |  4 +++
 drivers/pinctrl/freescale/pinctrl-vf610.c |  2 ++
 4 files changed, 63 insertions(+)

-- 
2.54.0