[PATCH v11] i2c: designware: defer probe if child GpioInt controllers are not bound

[Hardik Prakash <hardikprakash.official@gmail.com>]

I2C controllers may have child devices with GpioInt resources that
depend on GPIO controllers being fully initialized. If the I2C
controller probes and enumerates children before the referenced GPIO
controller has completed probe, GPIO interrupts may not be properly
configured, leading to device failures.

On Lenovo Yoga 7 14AGP11, the WACF2200 touchscreen (child of
AMDI0010:02) has a GpioInt resource pointing to GPIO 157 on the
pinctrl-amd controller (AMDI0030:00). When i2c-designware probes
AMDI0010:02 before pinctrl-amd finishes initializing, I2C transactions
fail with lost arbitration errors:

  0.285952  amd_gpio_probe: registering gpiochip  <- GPIO chip visible
  0.287121  amd_gpio_probe: requesting parent IRQ <- probe still running
  0.301454  AMDI0010:02 dw_i2c_plat_probe: start  <- races here
  2.348157  lost arbitration

Add a dependency check that walks ACPI child devices and defers probe
until any referenced GPIO controller is bound.

Fixes: 3812a9e84265 ("pinctrl-amd: enable IRQ for WACF2200 touchscreen on Lenovo Yoga 7 14AGP11")
Suggested-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Hardik Prakash <hardikprakash.official@gmail.com>
Assisted-by: Claude:claude-sonnet-5
Assisted-by: DeepSeek:deepseek-v4-pro
Link: https://bugzilla.kernel.org/show_bug.cgi?id=221494
---
 drivers/i2c/busses/i2c-designware-platdrv.c | 80 +++++++++++++++++++++
 1 file changed, 80 insertions(+)
v10 -> v11:
- Replaced custom gpio_controller_ref list with gpio_device_find_by_fwnode(),
  as suggested by Andy, dropping the linked list and dedup logic (~60 lines)
- Moved resource-skip explanation from commit message into a code comment
- Fixed device_is_bound() to check gpio_device_to_device(gdev)->parent
  rather than the gpio_device's own internal class device, which never
  has a driver bound to it


diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 6d6e81242f74..597aa9706364 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -8,12 +8,14 @@
  * Copyright (C) 2007 MontaVista Software Inc.
  * Copyright (C) 2009 Provigent Ltd.
  */
+#include <linux/acpi.h>
 #include <linux/clk-provider.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/err.h>
 #include <linux/errno.h>
+#include <linux/gpio/driver.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -130,6 +132,80 @@ static int i2c_dw_probe_lock_support(struct dw_i2c_dev *dev)
 	return 0;
 }
 
+#if defined(CONFIG_ACPI) && defined(CONFIG_GPIOLIB)
+/*
+ * Check whether an ACPI GpioInt resource's referenced GPIO controller
+ * has finished probing. Resources with no named controller (resource
+ * source string) are skipped, since they can't be resolved to a
+ * struct device.
+ */
+static int check_gpioint_resource(struct acpi_resource *ares, void *data)
+{
+	struct gpio_device *gdev __free(gpio_device_put) = NULL;
+	struct acpi_resource_gpio *agpio;
+	struct acpi_device *gpio_adev;
+	struct device *gpio_dev;
+	acpi_handle handle;
+
+	if (!acpi_gpio_get_irq_resource(ares, &agpio))
+		return 1; /* not a GpioInt resource, skip */
+
+	if (!agpio->resource_source.string_length)
+		return 1; /* no named controller, skip */
+
+	if (ACPI_FAILURE(acpi_get_handle(NULL, agpio->resource_source.string_ptr, &handle)))
+		return 1;
+
+	gpio_adev = acpi_fetch_acpi_dev(handle);
+	if (!gpio_adev)
+		return 1;
+
+	gdev = gpio_device_find_by_fwnode(acpi_fwnode_handle(gpio_adev));
+	if (!gdev)
+		return -EPROBE_DEFER; /* controller not registered yet: abort walk */
+
+	gpio_dev = gpio_device_to_device(gdev)->parent;
+	scoped_guard(device, gpio_dev) {
+		if (!device_is_bound(gpio_dev))
+			return -EPROBE_DEFER; /* controller not bound yet: abort walk */
+	}
+
+	return 1; /* bound, skip adding to resource list, continue walk */
+}
+
+static int check_child_gpioint(struct acpi_device *adev, void *data)
+{
+	struct list_head res_list;
+	int ret;
+
+	INIT_LIST_HEAD(&res_list);
+	ret = acpi_dev_get_resources(adev, &res_list, check_gpioint_resource, NULL);
+	acpi_dev_free_resource_list(&res_list);
+
+	/*
+	 * ret is a nonnegative resource count on success, which must not
+	 * be mistaken for a nonzero "stop iteration" signal by
+	 * acpi_dev_for_each_child(); only forward genuine errors.
+	 */
+	return ret < 0 ? ret : 0;
+}
+
+static int i2c_dw_check_gpio_dependencies(struct device *dev)
+{
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+
+	if (!adev)
+		return 0;
+
+	return acpi_dev_for_each_child(adev, check_child_gpioint, NULL);
+}
+#else
+static int i2c_dw_check_gpio_dependencies(struct device *dev)
+{
+	return 0;
+}
+#endif /* CONFIG_ACPI && CONFIG_GPIOLIB */
+
 static int dw_i2c_plat_probe(struct platform_device *pdev)
 {
 	u32 flags = (uintptr_t)device_get_match_data(&pdev->dev);
@@ -138,6 +214,10 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
 	struct dw_i2c_dev *dev;
 	int irq, ret;
 
+	ret = i2c_dw_check_gpio_dependencies(device);
+	if (ret)
+		return ret;
+
 	irq = platform_get_irq_optional(pdev, 0);
 	if (irq == -ENXIO)
 		flags |= ACCESS_POLLING;

base-commit: 58717b2a1365d06c8c64b72aa948541b53fe31eb
-- 
2.54.0