[kmac] Revise Entropy Timer register
Revised entropy timer register. It is split into two fields, wait timer
and entropy timer. Wait timer is for EDN request. If wait timer expires,
KMAC reports an error to the softaware.
Entropy timer is for update internal LFSR with newly fed seed from EDN
even the entropy is not consumed.
It also adds a few config fields, entropy ready and error processed.
Signed-off-by: Eunchan Kim <eunchan@opentitan.org>
diff --git a/hw/ip/kmac/data/kmac.hjson b/hw/ip/kmac/data/kmac.hjson
index ee2eedf..8a83597 100644
--- a/hw/ip/kmac/data/kmac.hjson
+++ b/hw/ip/kmac/data/kmac.hjson
@@ -213,6 +213,63 @@
Key Derivation Function (KDF).
'''
} // f: sideload
+ { bits: "17:16"
+ name: entropy_mode
+ desc: '''Entropy Mode
+
+ Software selects the entropy source with this field. In EdnMode,
+ the entropy generator sends requests to EDN to get the entropy. The
+ received entropy is fed into internal LFSR.
+
+ In SwMode, the software should update the internal LFSR seed
+ through !!ENTROPY_SEED_LOWER and !!ENTROPY_SEED_UPPER.
+ '''
+
+ enum: [
+ { value: "0"
+ name: "idle_mode"
+ desc: '''At reset state, the entropy mode is Idle mode. It does
+ not operate in this mode.
+ '''
+ }
+ { value: "1"
+ name: "edn_mode"
+ desc: "Entropy generator module fetches entropy from EDN"
+ }
+ { value: "2"
+ name: "sw_mode"
+ desc: '''Software update the internal entropy via register
+ interface'''
+ }
+ ]
+ } // f: entropy_mode
+ { bits: "19"
+ name: entropy_fast_process
+ desc: '''Entropy Fast process mode.
+
+ If 1, entropy logic uses garbage data while not processing the KMAC
+ key block. It will re-use previous entropy value and will not
+ expand the entropy when it is consumed. Only it refreshes the
+ entropy while processing the secret key block.
+ '''
+ } // f: entropy_fast_process
+ { bits: "24"
+ name: entropy_ready
+ desc: '''Entropy Ready status.
+
+ Software sets this field to allow the entropy generator in KMAC to
+ fetch the entropy and run.
+ '''
+ hwaccess: "hrw"
+ } // f: entropy_ready
+ { bits: "25"
+ name: err_processed
+ desc: '''When error occurs and one of the state machine stays at
+ Error handling state, SW may process the error based on
+ ERR_CODE, then let FSM back to the reset state
+ '''
+ hwaccess: "hrw"
+ } // f: err_processed
]
} // R: CFG
{ name: "CMD"
@@ -315,23 +372,34 @@
]
} // R: STATUS
{ name: "ENTROPY_PERIOD"
- desc: '''Entropy Refresh Period.
-
- This register determines the refresh period. The value is the number of
- clock cycles. In every entropy period, the entropy generation logic in
- KMAC requests new entropy to EDN and feed the value into LFSR seed.
-
- If 0, the entropy generation logic does not refresh its seed. The
- software manually updates the seed by writing into "ENTROPY_SEED"
- registers.
+ desc: '''Entropy Timer Periods.
'''
swaccess: "rw"
hwaccess: "hro"
regwen: "CFG_REGWEN"
fields: [
- { bits: "31:0"
- name: "period"
- desc: "entropy period in clock cycles"
+ { bits: "15:0"
+ name: "entropy_timer"
+ desc: '''Entropy period in clock cycles This register determines
+ the refresh period. The value is the number of clock cycles. In
+ every entropy period, the entropy generation logic in KMAC requests
+ new entropy to EDN and feed the value into LFSR seed.
+
+ If 0, the entropy generation logic does not refresh its seed. The
+ software manually updates the seed by writing into "ENTROPY_SEED"
+ registers. '''
+ }
+ { bits: "31:16"
+ name: "wait_timer"
+ desc: '''EDN request wait timer.
+
+ The entropy module in KMAC waits up to this field in clock cycles
+ after it sends request to EDN module. If the timer expires, the
+ entropy module moves to an error state and notifies to the system.
+
+ If 0, the entropy module waits the EDN response always. If EDN does
+ not respond in this configuration, the software shall reset the IP.
+ '''
}
]
} // R: ENTROPY_PERIOD
@@ -355,8 +423,9 @@
{ name: "ENTROPY_SEED_UPPER"
desc: '''Entropy Seed [63:32].
- Everytime when the software writes into this register, LFSR is reseeded
- with the value of {ENTROPY_SEED_UPPER, ENTROPY_SEED_LOWER}.
+ Everytime when the software writes into !!ENTROPY_SEED_LOWER register,
+ LFSR is reseeded with the value of {ENTROPY_SEED_UPPER,
+ ENTROPY_SEED_LOWER}.
'''
swaccess: "rw"
hwaccess: "hro"
