Re: [PATCH v5 4/6] reset: Instantiate reset GPIO controller for shared reset-gpios

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On 24/01/2024 08:45, Krzysztof Kozlowski wrote:
Devices sharing a reset GPIO could use the reset framework for
coordinated handling of that shared GPIO line.  We have several cases of
such needs, at least for Devicetree-based platforms.

If Devicetree-based device requests a reset line, while "resets"
Devicetree property is missing but there is a "reset-gpios" one,
instantiate a new "reset-gpio" platform device which will handle such
reset line.  This allows seamless handling of such shared reset-gpios
without need of changing Devicetree binding [1].

To avoid creating multiple "reset-gpio" platform devices, store the
Devicetree "reset-gpios" GPIO specifiers used for new devices on a
linked list.  Later such Devicetree GPIO specifier (phandle to GPIO
controller, GPIO number and GPIO flags) is used to check if reset
controller for given GPIO was already registered.

If two devices have conflicting "reset-gpios" property, e.g. with
different ACTIVE_xxx flags, this would allow to spawn two separate
"reset-gpio" devices, where the second would fail probing on busy GPIO

Link: [1]
Cc: Bartosz Golaszewski <brgl@xxxxxxxx>
Cc: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
Cc: Sean Anderson <sean.anderson@xxxxxxxx>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>


Depends on previous of change.
  drivers/reset/core.c             | 215 +++++++++++++++++++++++++++++--
  include/linux/reset-controller.h |   4 +
  2 files changed, 206 insertions(+), 13 deletions(-)

diff --git a/drivers/reset/core.c b/drivers/reset/core.c
index 4d5a78d3c085..60a8a33c4419 100644
--- a/drivers/reset/core.c
+++ b/drivers/reset/core.c


+	}
+	ret = __reset_add_reset_gpio_lookup(id, args->np, args->args[0],
+					    args->args[1]);

What would happen with gpio controllers using #gpio-cells = <3> (or more) like allwinner,sun4i-a10-pinctrl.yaml ?

On this example the flags are args->args[2] so this would probably fail.

This would also fails badly with #gpio-cells = <1>, args->args[1] value would be undefined.

You should probably limit to args->args_count == 2 for now.


+	if (ret < 0)
+		goto err_kfree;
+	rgpio_dev->of_args = *args;
+	/*
+	 * We keep the device_node reference, but is put at the end
+	 * of __of_reset_control_get(), so get it one more time.
+	 * Hold reference as long as rgpio_dev memory is valid.
+	 */
+	of_node_get(rgpio_dev->;
+	pdev = platform_device_register_data(NULL, "reset-gpio", id,
+					     &rgpio_dev->of_args,
+					     sizeof(rgpio_dev->of_args));


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