[PATCH v2 1/2] dm: core: read the device tree into plat data after pinctrl

[Mehmet Fide <mehmet.fide@gmail.com>]

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

device_probe() calls device_of_to_plat() before it applies the "default"
pinctrl state of the device, so a driver that acquires resources there
sees them undone by the pinctrl state that follows.

It has not always been that way. When the pinctrl uclass arrived in
commit d90a5a30dec1 ("pinctrl: add pin control uclass support") the
state was selected before ->ofdata_to_platdata() was called, and it
stayed that way for four years. Commit 29f7d05a347a ("dm: core: Move
ofdata_to_platdata() call earlier") then moved the call up so that the
platform data would be read before the device is probed, which is
reasonable in itself, but it also moved it above the pinctrl state,
which nothing asked for.

GPIOs are where this hurts. On most SoCs the direction of a pin lives in
the GPIO block, so a pinctrl state cannot disturb it, but on Vybrid the
output buffer enable is a bit of the pad register that pinctrl writes as
well. A fixed regulator asks for its enable GPIO in of_to_plat(), so the
pin is configured as an output and the pinctrl state of the same device
then turns it back into an input. The USB host VBUS regulator of a
Colibri VF50 is one of those: its pad reads 0x22ed once the regulator
has been probed, the value from the device tree, output buffer disabled,
and no USB device is ever powered.

Move the call back below the pinctrl step. That is also the order Linux
uses, and the order the board code of these boards used before the
driver model: set the pin muxing up first, then take the pin. The
pinctrl step itself cannot move up instead, because it relies on
DM_FLAG_ACTIVATED having been set to break the recursion described above
it.

Nothing between the two positions needs plat data: the parent probe, the
power domain and the pinctrl call all work off the device tree.

Tested with test/py on sandbox, before and after: 11 failed, 414 passed,
210 skipped, 1 xfailed, 20 errors, the same failures both times, all of
them from tools and images missing in my environment.

Tested on a Colibri VF50 V1.2A on an Iris carrier, U-Boot 2026.07 from
NAND: the pad of the VBUS pin reads 0x22ef after "usb start" instead of
0x22ed, a USB stick in the host port enumerates, and Linux still boots
with Ethernet, SD card and USB working.

Fixes: 29f7d05a347a ("dm: core: Move ofdata_to_platdata() call earlier")
Signed-off-by: Mehmet Fide <mehmet.fide@screeningeagle.com>
---
 drivers/core/device.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/core/device.c b/drivers/core/device.c
index 6024534ff93..ccdf0ab9220 100644
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -500,10 +500,6 @@ int device_probe(struct udevice *dev)
 	drv = dev->driver;
 	assert(drv);
 
-	ret = device_of_to_plat(dev);
-	if (ret)
-		goto fail;
-
 	/* Ensure all parents are probed */
 	if (dev->parent) {
 		ret = device_probe(dev->parent);
@@ -552,6 +548,10 @@ int device_probe(struct udevice *dev)
 				  dev->name, ret, errno_str(ret));
 	}
 
+	ret = device_of_to_plat(dev);
+	if (ret)
+		goto fail;
+
 	if (CONFIG_IS_ENABLED(IOMMU) && dev->parent &&
 	    (device_get_uclass_id(dev) != UCLASS_IOMMU)) {
 		ret = dev_iommu_enable(dev);
-- 
2.54.0