3.17-rc6 on ODROID: ERROR: Bad of_node_put() on /ehci at 12580000/port at 1

[Daniel Drake]

On Wed, Oct 1, 2014 at 12:36 AM, Vivek Gautam <gautam.vivek at samsung.com> wrote:
> One reason i doubt why it could be coming is because we are
> specifically putting the
> child after doing everything with it.
>
> When we are getting the child node using for_each_available_child_of_node(),
> which calls for of_get_next_available_child(). So of_get_next_available_child()
> does a of_node_put() on the "prev" node, in case we have siblings to the child.
>
> Can you see if the below change helps ?
>
> ------------------------------------------------------------------------------------------------------------
> diff --git a/drivers/usb/host/ehci-exynos.c b/drivers/usb/host/ehci-exynos.c
> index 7189f2e..1b726bf 100644
> --- a/drivers/usb/host/ehci-exynos.c
> +++ b/drivers/usb/host/ehci-exynos.c
> @@ -74,7 +74,6 @@ static int exynos_ehci_get_phy(struct device *dev,
>
>                 phy = devm_of_phy_get(dev, child, NULL);
>                 exynos_ehci->phy[phy_number] = phy;
> -               of_node_put(child);
>                 if (IS_ERR(phy)) {
>                         ret = PTR_ERR(phy);
>                         if (ret == -EPROBE_DEFER) {
> ------------------------------------------------------------------------------------------------------------
>
>
> This is on top of usb-next.
> If you are testing on rc6 only, then probably you will have to cherrypick two
> patches each for ehci-exynos and ohci-exynos:
> usb: host: ehci-exynos: Remove unnecessary usb-phy support
> usb: host: ohci-exynos: Remove unnecessary usb-phy support

I made the equivalent change to 3.17-rc7 (right now 3.17 is my main
interest), i.e. removed all of_node_put calls from
exynos_ehci_get_phy(). Same change is needed in exynos_ohci_get_phy().
Now the warnings are gone.
BTW, I think the warning only appeared when CONFIG_OF_SELFTEST=y

I didn't check the implementation details like you did, but I looked
at a few other users of for_each_available_child_of_node and it looks
like indeed you do not need to call of_node_put() on the children in
the normal case, or at least, nobody else does.

Thanks,
Daniel