[PATCH v2 4/7] driver core: fix automatic pinctrl management

[Johan Hovold <johan@kernel.org>]

Commit ab78029ecc34 ("drivers/pinctrl: grab default handles from device
core") added automatic pin-control management to driver core by looking
up and setting any default pinctrl state found in device tree while a
device is being probed.

This obviously runs into problems as soon as device-tree nodes are
reused for child devices which are later also probed as pins would
already have been claimed by the ancestor device.

For example if a USB host controller claims a pin, its root hub would
consequently fail to probe when its device-tree node is set to the node
of the controller:

    pinctrl-single 48002030.pinmux: pin PIN204 already requested by 48064800.ehci; cannot claim for usb1
    pinctrl-single 48002030.pinmux: pin-204 (usb1) status -22
    pinctrl-single 48002030.pinmux: could not request pin 204 (PIN204) from group usb_dbg_pins  on device pinctrl-single
    usb usb1: Error applying setting, reverse things back
    usb: probe of usb1 failed with error -22

Fix this by checking the new of_node_reused flag and skipping automatic
pinctrl configuration during probe if set.

Note that the flag is checked in driver core rather than in pinctrl
(e.g. in pinctrl_dt_to_map()) which would specifically have prevented
intentional use of a parent's pinctrl properties by a child device
(should such a need ever arise).

Fixes: ab78029ecc34 ("drivers/pinctrl: grab default handles from device core")
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/base/pinctrl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/base/pinctrl.c b/drivers/base/pinctrl.c
index 5917b4b5fb99..eb929dd6ef1e 100644
--- a/drivers/base/pinctrl.c
+++ b/drivers/base/pinctrl.c
@@ -23,6 +23,9 @@ int pinctrl_bind_pins(struct device *dev)
 {
 	int ret;
 
+	if (dev->of_node_reused)
+		return 0;
+
 	dev->pins = devm_kzalloc(dev, sizeof(*(dev->pins)), GFP_KERNEL);
 	if (!dev->pins)
 		return -ENOMEM;
-- 
2.13.0