[csrng/doc] Clarify application interface handshaking signals section

Previously, it wasn't clear that between the command request handshake
and the command response, the application interface wouldn't accept any
further commands including also uninstantiate commands.

Signed-off-by: Pirmin Vogel <[email protected]>
(cherry picked from commit 143c8e8)

Author: vogelpi

hw/ip/csrng/doc/theory_of_operation.md

@@ -308,16 +308,18 @@ This initial seed is tested to ensure some minimum quality for obfuscation use-
 
 #### Handshaking signals
 
-The application command signal `csrng_req_bus` is accompanied by a `csrng_valid_signal`, which is asserted by the requester when the command is valid.
-CSRNG may stall incoming commands by de-asserting the `csrng_req_ready` signal.
+The application interface signal `csrng_req_t` comprises a `csrng_req_valid` bit, which is asserted by the requester when the command request on `csrng_req_bus` is valid.
+CSRNG may stall incoming commands by de-asserting the `csrng_req_ready` bit of the `csrng_rsp_t` signal.
 A command is considered received whenever both `csrng_req_valid` and `csrng_req_ready` are asserted in the same clock cycle.
 
-Likewise a requester must only consider data on the `genbits` bus to be valid when the `genbits_valid` signal is asserted, and should assert `genbits_ready` whenever it is ready to accept the `genbits` data.
-The `genbits` data is considered successfully transmitted whenever `genbits_valid` and `genbits_ready` are asserted in the same clock cycle.
+Likewise a requester must only consider data on the `genbits_bus` signal to be valid when the `genbits_valid` signal is asserted, and should assert `genbits_ready` whenever it is ready to accept the data on `genbits_bus`.
+The `genbits_bus` data is considered successfully transmitted whenever `genbits_valid` and `genbits_ready` are asserted in the same clock cycle.
 
-A requester must always be ready to receive `csrng_req_sts` signals.
+A requester must always be ready to receive `csrng_rsp_ack` and `csrng_rsp_sts` signals.
 (There is no "ready" signal for command response messages sent to hardware.)
 
+**NOTE**: Between the command request handshake involving `csrng_req_valid/ready` and between signaling the command response on `csrng_rsp_ack/sts`, the application interface does not accept further commands.
+
 #### Waveforms
 
 ##### Application Interface: Instantiate Request
@@ -365,6 +367,11 @@ A requester must always be ready to receive `csrng_req_sts` signals.
 ]}
 ```
 
+**NOTE**: Between the command request handshake involving `csrng_req_valid/ready` and between signaling the command response on `csrng_rsp_ack/sts`, the application interface does not accept further commands including `uninstantiate` commands.
+For `generate` commands, this means the requestor has to first consume all entropy generated from the current command.
+Depending on the configuration of the system, this may take a very long time.
+For details on how to accelerate this process, refer to [Uninstantiating CSRNG through EDN](../../edn/doc/programmers_guide.md#uninstantiating-csrng-through-edn).
+
 ##### Application Interface:  Update Request
 
 ```wavejson