device tree binding documentation outdated

[Shawn Guo]

On Sat, Sep 28, 2013 at 09:38:59AM +0100, Russell King - ARM Linux wrote:
> Okay, the answer is that yes, GPR1 bit 21 should be clear on this version
> of the hardware, but there's plans to have the IMX6 generate the clock
> and remove the crystal for the AR8035.

Be careful, as mentioned in the reply to Matt, in that case, IMX6 can
only output the clock on pad GPIO_16, and the clock has to be externally
routed back to IMX6 on pad ENET_REF_CLK, so that ENET can get reference
clock for RGMII mode.

> Now, here's the question for the IMX6 maintainers: how do I avoid having
> GPR1 bit 21 set - it's unconditionally set by imx6q_1588_init() in
> arch/arm/mach-imx/mach-imx6q.c.  Moreover, how do I control this from
> DT?

GPR1[21] should be cleared only when there is a clock input on pad
GPIO_16 from external phy or oscillator.  Other than that, GPR1[21]
should always be set to loop the ENET_PLL clock back to ENET though
pad GPIO_16, for at least getting PTP (IEEE 1588) work, even in RGMII
mode.

So far, we haven't got any user with that setup (external phy or
oscillator generates clock to pad GPIO_16).  When we do, we can add a
device tree property for telling that.

Shawn