76 lines
2.9 KiB
ReStructuredText
76 lines
2.9 KiB
ReStructuredText
ibm,opal/power-mgt/occ device tree entries
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==========================================
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This node exports the per-chip pstate table properties to kernel.
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Example:
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.. code-block:: dts
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occ@7ffddf8000 {
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ibm,pstate-vdds = [45 45 46 46 46 47 48 49 4a 4b 4c 4d 4f 50 51 52 53 54 55 57 58 59 5a 5b 5c 5d 5e 5f 5f 60 61 62 63 64 65 65 66 67 68 69 6a 6a 6b 6c 6d 6e 6f 70 70 71];
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ibm,chip-id = <0x1>;
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phandle = <0x100003b8>;
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ibm,pstate-vcss = [3b 3d 3f 41 42 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 50 50 51 52 53 54 55 56 56 57 57 58 58 59 59 5a 5a 5b 5b 5c 5c 5d 5d 5e 5e 5f 5f 60 60 61 61 62 62];
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reg = <0x7f 0xfddf8000 0xb98>;
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};
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ibm,chip-id
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-----------
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This property denotes the ID of chip to which OCC belongs to.
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reg
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---
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This tuple gives the statring address of the OPAL data in HOMER and
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the size of the OPAL data.
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The top-level /ibm,opal/power-mgt contains : ::
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#size-cells = <1>
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#address-cells = <2>
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ibm,pstate-vcss ibm,pstate-vdds
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-------------------------------
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These properties list a voltage-identifier of each of the pstates listed in
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ibm,pstate-ids for the Vcs and Vdd values used for that pstate in that chip.
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Each VID is a single byte.
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ibm,opal/power-mgt/freq-domain-mask
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-----------------------------------
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This property is a bitmask which will have different value depending upon the
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generation of the processor. Frequency domain would indicate group of CPUs
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which would share same frequency. Bitwise AND is taken between this bitmask
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value and PIR of cpu. All the CPUs lying in the same frequency domain will have
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same result for AND. Thus frequency management can be done based on frequency
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domain. A frequency domain may be a core or a quad, etc depending upon the
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generation of the processor.
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For example, for POWER8 0xFFF8 indicates core wide frequency domain. Taking AND
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with the PIR of CPUs will yield us a frequency domain which is core wide
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distribution as last 3 bits have been masked which represent the threads.
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For POWER9, 0xFFF0 indicates quad wide frequency domain. Taking AND with
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the PIR of CPUs will yield us frequency domain which is quad wise
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distribution as last 4 bits have been masked which represent the cores.
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ibm,opal/power-mgt/domain-runs-at
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---------------------------------
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There are two strategies in which the OCC can change the frequency of the cores
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in the quad on P9.
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1) FREQ_MAX_IN_DOMAIN : the OCC sets the frequency of the quad to the maximum
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of the latest frequency requested by each of the component cores.
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2) FREQ_MOST_RECENTLY_SET : the OCC sets the frequency of the quad to the most
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recent frequency value requested by the CPUs in the quad
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In case of P8, the domain is the core and the strategy by default is
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FREQ_MOST_RECENTLY_SET since the PMCRs of the threads in the core are mirrored.
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However on P9, the domain is quad and the strategy is FREQ_MAX_IN_DOMAIN since
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each core has its own PMCR.
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domain-runs-at denotes the strategy which OCC is using to change the frequency
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of a frequency domain.
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