104 lines
3.2 KiB
Plaintext
104 lines
3.2 KiB
Plaintext
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NVIDIA Tegra cpufreq scaling tables
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This binding specifies format of scaling data for NVIDIA Tegra cpufreq driver.
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Required properties :
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- compatible : Must be one of the following
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"nvidia,tegra210-cpufreq"
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Optional properties:
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- status : standard DT availability property.
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Optional child nodes :
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- cpu-scaling-data : specifies cpufreq scaling table data for CPU clock.
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If this node is not present or not available, default frequency table
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constructed by the driver from CPU DVFS tables is used.
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- emc-scaling-data : specifies cpufreq scaling table data for EMC clock floor
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rate request based on CPU clock frequency.
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If the node is not present or not available, default EMC_TO_CPU limit ratio
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table hard-coded in the kernel is used.
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* cpu-scaling-data node properties.
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Required properties :
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- freq-table : array of frequencies converted to cpufreq driver targets as
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described below. Must be in kHz, in increasing order.
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Optional properties:
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- status : standard DT availability property.
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- preserve-across-suspend : if specified, cpufreq governor scaling limits are
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preserved during suspend/resume operations; if not present, cpufreq governor
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scaling limits are set to frequency defined in tegra suspend platform data
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during suspend/resume operations.preserve_cpu_speed
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- clip-to-dvfs-down : if specified, freq-table entries are clipped down to CPU
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DVFS table; if not present, freq-table entries are clipped up to CPU DVFS
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table.
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Conversion from freq-table entries to cpufreq driver targets:
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If clip-to-dvfs-down property is present:
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any freq-table entry below bottom DVFS step is kept unchanged
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any freq-table entry exactly at one of the DVFS steps is kept unchanged
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any freq-table entry between two DVFS steps is replaced with lower step
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any freq-table entry above top DVFS step is replaced with top step
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If clip-to-dvfs-down property is not present:
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any freq-table entry below bottom DVFS step is replaced with bottom step
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any freq-table entry exactly at one of the DVFS steps is kept unchanged
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any freq-table entry between two DVFS steps is replaced with upper step
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any freq-table entry above top DVFS step is replaced with top step
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* emc-scaling-data node properties.
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Required properties :
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- emc-cpu-limit-table : array of frequencies to specify EMC and CPU rates
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relation as described below:
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if F[0] > CPU frequency, then EMC frequency is unrestricted by CPU
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if F[i+2] > CPU frequency >= F[i], then EMC frequency >= F[i+1],
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i = 0, ... N-4
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if CPU frequency >= F[N-2], then EMC frequency >= F[N-1]
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N is array size, must be even
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i = 0 ... N-1 is 0-based position index within array
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F[i] value of array cell at index i
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All frequencies are in kHz. CPU frequencies at even positions must be in
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increasing order. EMC frequencies at odd positions are clipped down to EMC
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maximum rate.
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Optional properties:
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- status : standard DT availability property.
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Example:
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cpufreq {
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compatible = "nvidia,tegra210-cpufreq";
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cpu-scaling-data {
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freq-table = <
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200000
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300000
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800000
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1000000
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1500000
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2000000
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2100000
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>;
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};
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emc-scaling-data {
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emc-cpu-limit-table = <
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/* CPU EMC */
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100000 95000
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200000 185000
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300000 375000
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800000 550000
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1000000 750000
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1500000 1600000
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>;
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};
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};
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