[aes/rtl] Correct generation of idle signal in manual operation mode

Signed-off-by: Pirmin Vogel <[email protected]>

hw/ip/aes/rtl/aes_control_fsm.sv

@@ -258,9 +258,11 @@ module aes_control_fsm
   assign gcm_tag = (mode_i == AES_GCM) & (gcm_phase_i == GCM_TAG);
   assign start_gcm_tag = gcm_tag & data_in_new;
 
-  // The GHASH block is idle whenever it's ready to receive inputs and where not about to start
-  // a GCM related operation.
-  assign ghash_idle = ghash_in_ready_i & ~(start_gcm_init | start_gcm | start_gcm_tag);
+  // The GHASH block is idle whenever it's ready to receive inputs and we're not about to start
+  // a GCM related operation. For simplicity, the latter condition is not factored into the
+  // ghash_idle signal but into the idle signal directly. This is done via the start signal,
+  // meaning also invalid configurations, alerts and manual operation get handled correctly.
+  assign ghash_idle = ghash_in_ready_i;
 
   // In GCM, the counter performs inc32() instead of inc128(), i.e., the counter wraps at 32 bits.
   assign ctr_inc32_o = (mode_i == AES_GCM);