Messages in this thread | | | Date | Thu, 25 Sep 2014 12:56:34 -0700 | From | Florian Fainelli <> | Subject | Re: GPIO registration for external Ethernet PHY oscillator enable/disable |
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On 09/25/2014 12:17 PM, Michael Welling wrote: > Looks like my original message got buried in the mailing list. > > Lets try this again with a few key developers CC'd. > > Original Message: > I have some questions that span multiple subsystems including > gpio/pinctrl, apm, and net subsystems. > > On some of our system on module designs, we use a GPIO to toggle the > enable pin on external oscillators. In particular, we are using a 50Mhz > oscillator to drive a clock on a RMII Ethernet PHY. > > Though I can configure the pin such that the Ethernet interface works we > are looking to disable the oscillator during APM sleep but after the PHY > is put into a low power mode. > > How do I register a GPIO for use in the PHY suspend and resume code?
So, PHY drivers are allowed to provide specialized implementations for suspend/resume operations that are called by phy_suspend() and phy_resume(), the current Micrel PHY driver uses the generic suspend/resume implementation and it is best if we can keep doing that.
> Can it be handled outside of the PHY driver?
I see a few possible options:
- hook a pm_runtime callbacks for your platform, check the device pointer to make sure this is the PHY device, and when that is the case, toggle the GPIO accordingly
- add an additional "osc_gpio" configuration parameter passed to the Ethernet MAC driver (presumably drivers/net/ethernet/cadence/macb.c?) and toggle the GPIO before and after the calls to the PHY state machine (phy_suspend, phy_resume, phy_start, phy_stop), that might be simpler
- last but not least, make the PHY driver aware of that optional GPIO, create customized PHY suspend/resume/config_aneg callbacks
> If so how do ensure the appropriate suspend and resume sequencing? > > For reference, we are using a Micrel KSZ8081 PHY connected to a > AT91SAMA5D35 processor. > > 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. > > Is there a way to directly change the state of a GPIO pin from a > devicetree entry? >
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