diff --git a/doc/opal-api/opal-imc-counters.rst b/doc/opal-api/opal-imc-counters.rst
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+.. _opal-imc-counters:
+
+OPAL_IMC_COUNTERS_INIT
+==============================
+OPAL call interface to initialize In-memory collection
+infrastructure. Call does multiple scom writes on each
+incavation for Core IMC initialization. And for the
+Nest IMC, at this point, call is a no-op and returns
+OPAL_SUCCESS. Incase of kexec, OS driver should first
+stop the engine via OPAL_IMC_COUNTER_STOP(and then
+free the memory if allocated, for nest memory is
+mmapped). Incase of kdump, OS driver should stop
+the engine via OPAL_IMC_COUNTER_STOP.
+
+OPAL does sanity checks to detect unknown or
+unsupported IMC device type and nest units.
+check_imc_device_type() function removes
+unsupported IMC device type. disable_unavailable_units()
+removes unsupported nest units by the microcode.
+This way OPAL can lock down and advertise only
+supported device type and nest units.
+
+Parameters
+----------
+``uint32_t type``
+  This parameter specifies the imc counter domain.
+  The value should be 'OPAL_IMC_COUNTERS_CORE'
+
+``uint64_t addr``
+  This parameter must have a non-zero value.
+  This value must be a physical address of the core.
+
+``uint64_t cpu_pir``
+  This parameter specifices target cpu pir
+
+Returns
+-------
+OPAL_PARAMETER - In case of  unsupported ``type``
+OPAL_HARDWARE  - If any error in setting up the hardware.
+OPAL_SUCCESS   - On succesfully initialized or even if init operation is a no-op.
+
+
+OPAL_IMC_COUNTERS_START
+============================
+OPAL call interface for starting the In-Memory Collection
+counters for a specified domain (NEST/CORE).
+
+Parameters
+----------
+``uint32_t type``
+ This parameter specifies the imc counter domain.
+ The value can be either 'OPAL_IMC_COUNTERS_NEST'
+ or 'OPAL_IMC_COUNTERS_CORE'
+
+``uint64_t cpu_pir``
+  This parameter specifices target cpu pir
+
+Returns
+-------
+OPAL_PARAMETER - In case of  Unsupported ``type``
+OPAL_HARDWARE  - If any error in setting up the hardware.
+OPAL_SUCCESS   - On successful execution of the operation for the given ``type``.
+
+
+OPAL_IMC_COUNTERS_STOP
+===========================
+OPAL call interface for stoping In-Memory
+Collection counters for a specified domain (NEST/CORE).
+STOP should always be called after a related START.
+While STOP *may* run successfully without an associated
+START call, this is not gaurenteed.
+
+Parameters
+----------
+``uint32_t type``
+ This parameter specifies the imc counter domain.
+ The value can be either 'OPAL_IMC_COUNTERS_NEST'
+ or 'OPAL_IMC_COUNTERS_CORE'
+
+``uint64_t cpu_pir``
+  This parameter specifices target cpu pir
+
+Returns
+-------
+OPAL_PARAMETER - In case of  Unsupported ``type``
+OPAL_HARDWARE  - If any error in setting up the hardware.
+OPAL_SUCCESS   - On successful execution of the operation for the given ``type``.