Messages in this thread | | | Date | Tue, 7 Oct 2014 16:04:27 +0200 | Subject | Re: GPIO registration for external Ethernet PHY oscillator enable/disable | From | Linus Walleij <> |
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On Thu, Sep 25, 2014 at 9:17 PM, Michael Welling <mwelling@emacinc.com> wrote:
> How do I register a GPIO for use in the PHY suspend and resume code? > Can it be handled outside of the PHY driver?
Nominally these days you should get a named GPIO using the GPIO descriptor abstraction, putting a named GPIO reference in the device tree node for the PHY, which should work fine if you're using device tree for this system. Documentation/gpio/consumer.txt
> If so how do ensure the appropriate suspend and resume sequencing?
AFAICT there is no good answer to this kind of questions. I guess my best answer would be something like what has been said for DRM drivers: handle all the sequence-sensitive hardware in one big composite driver and handle sequencing in the driver.
> For reference, we are using a Micrel KSZ8081 PHY connected to a > AT91SAMA5D35 processor.
I don't know how AT91 is progressing on the device tree side or if it's strictly required to boot these days. If it is, you should be able to proceed as indicated.
> Addendum: > I ran into another situation where a GPIO enabled oscillator was used. > The oscillator in this case drives the master clock for a audio codec. > In the old days (before device tree), I could initialize the GPIO in the > platform board file. Now with device tree I can setup the pin multipler > but the initial state of the GPIO I am not sure how to set.
A driver needs to do this. Like a drivers/clk driver in this case I guess?
> Is there a way to directly change the state of a GPIO pin from a > devicetree entry?
I have suggested mechanisms like GPIO hogs to replace the need for very basic drivers that would just take a GPIO during init, set it and never do anything with it.
Like the gpiochip node should have some hog entries:
gpio-hog-high = <0>, <1>, <2>...; gpio-hog-low = <...>;
Then they would be taken away from other consumers and not possible to use for anything.
This has so far not been implemented though.
Yours, Linus Walleij
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