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dm: core: Add a comment about pinctrl_select_state()

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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>
This commit is contained in:
Simon Glass 2021-01-21 13:57:13 -07:00
parent 0dc2bf2b6e
commit 017d421828
1 changed files with 9 additions and 0 deletions
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9
drivers/core/device.c
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@ -462,6 +462,15 @@ int device_probe(struct udevice *dev)
* continue regardless of the result of pinctrl. Don't process pinctrl * continue regardless of the result of pinctrl. Don't process pinctrl
* settings for pinctrl devices since the device may not yet be * settings for pinctrl devices since the device may not yet be
* probed. * 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) if (dev->parent && device_get_uclass_id(dev) != UCLASS_PINCTRL)
pinctrl_select_state(dev, "default"); pinctrl_select_state(dev, "default");