Messages in this thread | | | Date | Sun, 30 Aug 2009 14:51:57 +0200 | Subject | Re: [PATCH] AB3100 regulator support v1 | From | Linus Walleij <> |
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2009/8/30 Mark Brown <broonie@opensource.wolfsonmicro.com>:
> [While setting up a child platform device from a platform driver > probe...] > >> >> + /* This would seem logical but makes everything break... */ >> >> + /* pdev->dev.parent = parent; */ > >> > Err... it does? In what way? > >> The sub-platform devices are added, but when I add a platform driver for >> them, the probing does not commence, because they hang in >> driver base/dd.c: __driver_attach() trying to take the parent semaphore, >> i.e. this line: > >> if (dev->parent) /* Needed for USB */ >> down(&dev->parent->sem); > >> In this case the parent is ab3100-regulators, the platform device for >> the set of regulators. > > On the face of it (and without having actually looked at a running > system or anything yet) I'm rather surprised that platform based MFD > drivers aren't running into this issue more often. CCing in Alan who > made the change.
I think it hasn't happened a lot because most MFD:s spawn their platform device children at subsystem_init and then register drivers for them at driver_init. E.g. all the wm8350 children have their drivers at higher init levels, except for the regulators which are by chance saved by having the i2c device as parent.
> However, fixing this is not required to avoid the issue for this > particular driver. The problem is being caused because in addition to > the core MFD driver for the device you've chosen to create both a > platform device covering all regulators and further per-regulator child > platform devices.
Yeah I know, I thought it was elegant... :-/
> If you create only one level of child device for the > MFD you'll avoid the issue because your core device is an I2C device. > Either have a device per regulator or have a single device which > registers multiple regulators.
Yep I elaborated registering multiple regulators to the ab3100-regulators platform device, I'll try this.
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