NVIDIA Tegra cpufreq scaling tables

This binding specifies format of scaling data for NVIDIA Tegra cpufreq driver.

Required properties :
- compatible : Must be one of the following
        "nvidia,tegra210-cpufreq"

Optional properties:
- status : standard DT availability property.

Optional  child nodes :
- cpu-scaling-data : specifies cpufreq scaling table data for CPU clock.
  If this node is not present or not available, default frequency table
  constructed by the driver from CPU DVFS tables is used.
- emc-scaling-data : specifies cpufreq scaling table data for EMC clock floor
  rate request based on CPU clock frequency.
  If the node is not present or not available, default EMC_TO_CPU limit ratio
  table hard-coded in the kernel is used.


* cpu-scaling-data node properties.

Required properties :
- freq-table : array of frequencies converted to cpufreq driver targets as
  described below. Must be in kHz, in increasing order.

Optional properties:
- status : standard DT availability property.
- preserve-across-suspend : if specified, cpufreq governor scaling limits are
  preserved during suspend/resume operations; if not present, cpufreq governor
  scaling limits are set to frequency defined in tegra suspend platform data
  during suspend/resume operations.preserve_cpu_speed
- clip-to-dvfs-down : if specified, freq-table entries are clipped down to CPU
  DVFS table; if not present, freq-table entries are clipped up to CPU DVFS
  table.

  Conversion from freq-table entries to cpufreq driver targets:

  If clip-to-dvfs-down property is present:
  any freq-table entry below bottom DVFS step is kept unchanged
  any freq-table entry exactly at one of the DVFS steps is kept unchanged
  any freq-table entry between two DVFS steps is replaced with lower step
  any freq-table entry above top DVFS step is replaced with top step

  If clip-to-dvfs-down property is not present:
  any freq-table entry below bottom DVFS step is replaced with bottom step
  any freq-table entry exactly at one of the DVFS steps is kept unchanged
  any freq-table entry between two DVFS steps is replaced with upper step
  any freq-table entry above top DVFS step is replaced with top step


* emc-scaling-data node properties.

Required properties :
- emc-cpu-limit-table : array of frequencies to specify EMC and CPU rates
  relation as described below:

	if F[0] > CPU frequency, then EMC frequency is unrestricted by CPU
	if F[i+2] > CPU frequency >= F[i], then EMC frequency >= F[i+1],
	i = 0, ... N-4
	if CPU frequency >= F[N-2], then EMC frequency >= F[N-1]

	N is array size, must be even
	i = 0 ... N-1 is 0-based position index within array
	F[i] value of array cell at index i

   All frequencies are in kHz. CPU frequencies at even positions must be in
   increasing order. EMC frequencies at odd positions are clipped down to EMC
   maximum rate.

Optional properties:
- status : standard DT availability property.


Example:

cpufreq {
	compatible = "nvidia,tegra210-cpufreq";
	cpu-scaling-data {
		freq-table = <
			200000
			300000
			800000
			1000000
			1500000
			2000000
			2100000
		>;
	};

	emc-scaling-data {
		emc-cpu-limit-table = <
			/* CPU    EMC */
			100000  95000
			200000  185000
			300000  375000
			800000  550000
			1000000 750000
			1500000	1600000
		>;
	};
};