[kmac] Change fifo_empty interrupt type to status

This resolves #21049. Signed-off-by: Pirmin Vogel <[email protected]>
lowRISC · Feb 26, 2024 · 6645b60 · 6645b60
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diff --git a/hw/ip/kmac/data/kmac.hjson b/hw/ip/kmac/data/kmac.hjson
@@ -45,7 +45,13 @@
       desc: "KMAC/SHA3 absorbing has been completed"
     }
     { name: "fifo_empty"
-      desc: "Message FIFO empty condition"
+      type: "status"
+      desc: '''
+            The message FIFO is empty.
+            This interrupt is not raised or de-asserts if any of the following conditions are met:
+            1) The KMAC block is exercised by a hardware application interface.
+            2) The KMAC block is completely idle, e.g., after finishing an operation.
+            '''
     }
     { name: "kmac_err"
       desc: "KMAC/SHA3 error occurred. ERR_CODE register shows the details"

diff --git a/hw/ip/kmac/doc/interfaces.md b/hw/ip/kmac/doc/interfaces.md
@@ -22,11 +22,11 @@ Referring to the [Comportable guideline for peripheral device functionality](htt
 
 ## Interrupts
 
-| Interrupt Name   | Type   | Description                                                   |
-|:-----------------|:-------|:--------------------------------------------------------------|
-| kmac_done        | Event  | KMAC/SHA3 absorbing has been completed                        |
-| fifo_empty       | Event  | Message FIFO empty condition                                  |
-| kmac_err         | Event  | KMAC/SHA3 error occurred. ERR_CODE register shows the details |
+| Interrupt Name   | Type   | Description                                                                                                                                                                                                                                                     |
+|:-----------------|:-------|:----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| kmac_done        | Event  | KMAC/SHA3 absorbing has been completed                                                                                                                                                                                                                          |
+| fifo_empty       | Status | The message FIFO is empty. This interrupt is not raised or de-asserts if any of the following conditions are met: 1) The KMAC block is exercised by a hardware application interface. 2) The KMAC block is completely idle, e.g., after finishing an operation. |
+| kmac_err         | Event  | KMAC/SHA3 error occurred. ERR_CODE register shows the details                                                                                                                                                                                                   |
 
 ## Security Alerts
 

diff --git a/hw/ip/kmac/doc/registers.md b/hw/ip/kmac/doc/registers.md
@@ -78,15 +78,27 @@ Interrupt State Register
 ### Fields
 
 ```wavejson
-{"reg": [{"name": "kmac_done", "bits": 1, "attr": ["rw1c"], "rotate": -90}, {"name": "fifo_empty", "bits": 1, "attr": ["rw1c"], "rotate": -90}, {"name": "kmac_err", "bits": 1, "attr": ["rw1c"], "rotate": -90}, {"bits": 29}], "config": {"lanes": 1, "fontsize": 10, "vspace": 120}}
+{"reg": [{"name": "kmac_done", "bits": 1, "attr": ["rw1c"], "rotate": -90}, {"name": "fifo_empty", "bits": 1, "attr": ["ro"], "rotate": -90}, {"name": "kmac_err", "bits": 1, "attr": ["rw1c"], "rotate": -90}, {"bits": 29}], "config": {"lanes": 1, "fontsize": 10, "vspace": 120}}
 ```
 
-|  Bits  |  Type  |  Reset  | Name       | Description                                                   |
-|:------:|:------:|:-------:|:-----------|:--------------------------------------------------------------|
-|  31:3  |        |         |            | Reserved                                                      |
-|   2    |  rw1c  |   0x0   | kmac_err   | KMAC/SHA3 error occurred. ERR_CODE register shows the details |
-|   1    |  rw1c  |   0x0   | fifo_empty | Message FIFO empty condition                                  |
-|   0    |  rw1c  |   0x0   | kmac_done  | KMAC/SHA3 absorbing has been completed                        |
+|  Bits  |  Type  |  Reset  | Name                                  |
+|:------:|:------:|:-------:|:--------------------------------------|
+|  31:3  |        |         | Reserved                              |
+|   2    |  rw1c  |   0x0   | [kmac_err](#intr_state--kmac_err)     |
+|   1    |   ro   |   0x0   | [fifo_empty](#intr_state--fifo_empty) |
+|   0    |  rw1c  |   0x0   | [kmac_done](#intr_state--kmac_done)   |
+
+### INTR_STATE . kmac_err
+KMAC/SHA3 error occurred. ERR_CODE register shows the details
+
+### INTR_STATE . fifo_empty
+The message FIFO is empty.
+This interrupt is not raised or de-asserts if any of the following conditions are met:
+1) The KMAC block is exercised by a hardware application interface.
+2) The KMAC block is completely idle, e.g., after finishing an operation.
+
+### INTR_STATE . kmac_done
+KMAC/SHA3 absorbing has been completed
 
 ## INTR_ENABLE
 Interrupt Enable Register

diff --git a/hw/ip/kmac/dv/env/kmac_scoreboard.sv b/hw/ip/kmac/dv/env/kmac_scoreboard.sv
@@ -663,7 +663,6 @@ class kmac_scoreboard extends cip_base_scoreboard #(
         if (data_phase_write) begin
           // clear internal state on a write
           if (item.a_data[KmacDone])      intr_kmac_done = 0;
-          if (item.a_data[KmacFifoEmpty]) intr_fifo_empty = 0;
           if (item.a_data[KmacErr])       intr_kmac_err = 0;
         end else if (data_phase_read) begin
           // ICEBOX: check below

diff --git a/hw/ip/kmac/rtl/kmac.sv b/hw/ip/kmac/rtl/kmac.sv
@@ -582,8 +582,6 @@ module kmac
   // Interrupt //
   ///////////////
 
-  logic event_msgfifo_empty, msgfifo_empty_q;
-
   // Hash process absorbed interrupt
   // Convert mubi4_t to logic to generate interrupts
   assign event_absorbed = prim_mubi_pkg::mubi4_test_true_strict(app_absorbed);
@@ -605,17 +603,22 @@ module kmac
     $rose(prim_mubi_pkg::mubi4_test_true_strict(sha3_absorbed)) |=>
       prim_mubi_pkg::mubi4_test_false_strict(sha3_absorbed))
 
-  always_ff @(posedge clk_i or negedge rst_ni) begin
-    if (!rst_ni) msgfifo_empty_q <= 1'b1;
-    else         msgfifo_empty_q <= msgfifo_empty;
-  end
-
-  assign event_msgfifo_empty = ~msgfifo_empty_q & msgfifo_empty;
-
-  prim_intr_hw #(.Width(1)) intr_fifo_empty (
+  // Message FIFO empty interrupt
+  // The message FIFO empty interrupt is not useful for software if:
+  // - One of the hardware application interfaces is actively using the KMAC block. In this case
+  //   the message FIFO including the empty condition is managed entirely by the application
+  //   interface.
+  // - The KMAC block is completely idle. The FIFO should anyway be empty in that case.
+  logic status_msgfifo_empty;
+  assign status_msgfifo_empty = msgfifo_empty & ~app_active & (sha3_fsm != sha3_pkg::StIdle);
+
+  prim_intr_hw #(
+    .Width(1),
+    .IntrT("Status")
+  ) intr_fifo_empty (
     .clk_i,
     .rst_ni,
-    .event_intr_i           (event_msgfifo_empty),
+    .event_intr_i           (status_msgfifo_empty),
     .reg2hw_intr_enable_q_i (reg2hw.intr_enable.fifo_empty.q),
     .reg2hw_intr_test_q_i   (reg2hw.intr_test.fifo_empty.q),
     .reg2hw_intr_test_qe_i  (reg2hw.intr_test.fifo_empty.qe),

diff --git a/hw/ip/kmac/rtl/kmac_reg_top.sv b/hw/ip/kmac/rtl/kmac_reg_top.sv
@@ -181,7 +181,6 @@ module kmac_reg_top (
   logic intr_state_kmac_done_qs;
   logic intr_state_kmac_done_wd;
   logic intr_state_fifo_empty_qs;
-  logic intr_state_fifo_empty_wd;
   logic intr_state_kmac_err_qs;
   logic intr_state_kmac_err_wd;
   logic intr_enable_we;
@@ -418,16 +417,16 @@ module kmac_reg_top (
   //   F[fifo_empty]: 1:1
   prim_subreg #(
     .DW      (1),
-    .SwAccess(prim_subreg_pkg::SwAccessW1C),
+    .SwAccess(prim_subreg_pkg::SwAccessRO),
     .RESVAL  (1'h0),
     .Mubi    (1'b0)
   ) u_intr_state_fifo_empty (
     .clk_i   (clk_i),
     .rst_ni  (rst_ni),
 
     // from register interface
-    .we     (intr_state_we),
-    .wd     (intr_state_fifo_empty_wd),
+    .we     (1'b0),
+    .wd     ('0),
 
     // from internal hardware
     .de     (hw2reg.intr_state.fifo_empty.de),
@@ -2846,8 +2845,6 @@ module kmac_reg_top (
 
   assign intr_state_kmac_done_wd = reg_wdata[0];
 
-  assign intr_state_fifo_empty_wd = reg_wdata[1];
-
   assign intr_state_kmac_err_wd = reg_wdata[2];
   assign intr_enable_we = addr_hit[1] & reg_we & !reg_error;
 

diff --git a/sw/device/lib/dif/autogen/dif_kmac_autogen.c b/sw/device/lib/dif/autogen/dif_kmac_autogen.c
@@ -73,7 +73,7 @@ static bool kmac_get_irq_bit_index(dif_kmac_irq_t irq,
 
 static dif_irq_type_t irq_types[] = {
     kDifIrqTypeEvent,
-    kDifIrqTypeEvent,
+    kDifIrqTypeStatus,
     kDifIrqTypeEvent,
 };
 

diff --git a/sw/device/lib/dif/autogen/dif_kmac_autogen.h b/sw/device/lib/dif/autogen/dif_kmac_autogen.h
@@ -89,7 +89,10 @@ typedef enum dif_kmac_irq {
    */
   kDifKmacIrqKmacDone = 0,
   /**
-   * Message FIFO empty condition
+   * The message FIFO has run empty. This interrupt is not raised or de-asserts
+   * if any of the following conditions are met: 1) The KMAC block is exercised
+   * by a hardware application interface. 2) The KMAC block is completely idle,
+   * e.g., after finishing an operation.
    */
   kDifKmacIrqFifoEmpty = 1,
   /**