Re: device tree binding documentation outdated

[Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>]

On Fri, Oct 04, 2013 at 11:45:39PM +0800, Shawn Guo wrote:
> On Thu, Oct 03, 2013 at 12:49:11AM +0100, Russell King - ARM Linux wrote:
> > RGMII mode.
> > 
> > In current hardware, the phy has its own 25MHz crystal.  This provides
> > the phy with its clocks, and the phy itself contains a PLL, which it
> > uses to generate 125MHz.
> > 
> > The phy can be (and is) configured to generate this 125MHz clock on
> > the CLK_25M pin, which is connected to the IMX6 ENET_REF_CLK pad (V22
> > ball).
> > 
> > Hence, we have in DT:
> > 	MX6QDL_PAD_ENET_REF_CLK__ENET_TX_CLK
> > 
> > So far, so good. 
> > 
> > 
> > On current hardware, GPIO 16 is not connected to anything except some
> > 0402 resistor pads where the resistor is not fitted.  On future hardware,
> > the above crystal will be removed, and the appropriate 0402 resistor
> > placed to supply a clock provided on GPIO 16 to the phy.
> > 
> > Hence, to support both hardware configurations transparently, GPIO 16
> > should be configured to generate a 25MHz clock for use by the phy.
> 
> On AR8035 XTLI pin?  Here is what I read from AR8035 data sheet.
> 
> XTLI (Analog input signal): Crystal oscillator input. Requires a 27 pF
> capacitor to GND.  Support external 25 MHz, 1.2V swing clock input
> through this pin.
> 
> XTLO (Analog output signal): Crystal oscillator output; 27 pF to GND.
> 
> Will AR8035 just work if we provide a digital 25Mhz clock (from GPIO_16)
> on its XTLI pin?

Well, "Support external 25 MHz, 1.2V swing clock input through this pin."
suggests the answer is yes.  The characterists suggest that if the supplied
clock is within -0.3 to 0.15V for the low level, and 0.8 to 1.5V for the
high level, it should work.
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