dm: core: Add a comment about pinctrl_select_state()

The use of pinctrl in the core of driver model is useful but can provoke
some strange behaviour. Add a comment to aid debugging.

Signed-off-by: Simon Glass <sjg@chromium.org>

diff --git a/drivers/core/device.c b/drivers/core/device.c
index aeab383..8629df8 100644 (file)
--- a/drivers/core/device.c
+++ b/drivers/core/device.c
@@ -462,6 +462,15 @@ int device_probe(struct udevice *dev)
         * continue regardless of the result of pinctrl. Don't process pinctrl
         * settings for pinctrl devices since the device may not yet be
         * probed.
+        *
+        * This call can produce some non-intuitive results. For example, on an
+        * x86 device where dev is the main PCI bus, the pinctrl device may be
+        * child or grandchild of that bus, meaning that the child will be
+        * probed here. If the child happens to be the P2SB and the pinctrl
+        * device is a child of that, then both the pinctrl and P2SB will be
+        * probed by this call. This works because the DM_FLAG_ACTIVATED flag
+        * is set just above. However, the PCI bus' probe() method and
+        * associated uclass methods have not yet been called.
         */
        if (dev->parent && device_get_uclass_id(dev) != UCLASS_PINCTRL)
                pinctrl_select_state(dev, "default");