[silicon_creator,ibex,rnd] Introduce mock for ibex, use it in rnd

In order to properly test the rnd library, introduce a mock for the
ibex library. This allows to better test the rnd code without knowing
the specific implementation.

Signed-off-by: Amaury Pouly <[email protected]>

Author: pamaury

sw/device/silicon_creator/lib/drivers/BUILD

@@ -261,13 +261,19 @@ opentitan_test(
 dual_cc_library(
     name = "ibex",
     srcs = dual_inputs(
-        host = ["ibex_host.c"],
-        shared = ["ibex.c"],
+        device = ["ibex.c"],
+        host = ["mock_ibex.cc"],
     ),
     hdrs = dual_inputs(
+        host = ["mock_ibex.h"],
         shared = ["ibex.h"],
     ),
     deps = dual_inputs(
+        host = [
+            "//sw/device/lib/base:global_mock",
+            "//sw/device/silicon_creator/testing:rom_test",
+            "@googletest//:gtest",
+        ],
         shared = [
             "//hw/top:rv_core_ibex_c_regs",
             "//hw/top:dt",
@@ -620,6 +626,7 @@ dual_cc_library(
             "@googletest//:gtest",
         ],
         shared = [
+            ":ibex",
             ":lifecycle",
             "//sw/device/lib/base:macros",
             "//sw/device/silicon_creator/lib:error",

sw/device/silicon_creator/lib/drivers/ibex_host.c

@@ -0,0 +1,18 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "sw/device/silicon_creator/lib/drivers/mock_ibex.h"
+
+namespace rom_test {
+extern "C" {
+uint32_t ibex_mcycle32(void) { return MockIbex::Instance().MCycle32(); }
+uint64_t ibex_mcycle(void) { return MockIbex::Instance().MCycle(); }
+
+uint64_t ibex_time_to_cycles(uint64_t time_us) {
+  return MockIbex::Instance().IbexTimeToCycles(time_us);
+}
+
+uint32_t ibex_rnd32_read(void) { return MockIbex::Instance().Rnd32(); }
+}
+}  // namespace rom_test

sw/device/silicon_creator/lib/drivers/mock_ibex.cc

@@ -0,0 +1,32 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_DRIVERS_MOCK_IBEX_H_
+#define OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_DRIVERS_MOCK_IBEX_H_
+
+#include "sw/device/lib/base/global_mock.h"
+#include "sw/device/silicon_creator/lib/drivers/ibex.h"
+#include "sw/device/silicon_creator/testing/rom_test.h"
+
+namespace rom_test {
+namespace internal {
+
+/**
+ * Mock class for ibex.c.
+ */
+class MockIbex : public global_mock::GlobalMock<MockIbex> {
+ public:
+  MOCK_METHOD(uint32_t, Rnd32, ());
+  MOCK_METHOD(uint32_t, MCycle32, ());
+  MOCK_METHOD(uint64_t, MCycle, ());
+  MOCK_METHOD(uint64_t, IbexTimeToCycles, (uint64_t time_us));
+};
+
+}  // namespace internal
+
+using MockIbex = testing::StrictMock<internal::MockIbex>;
+
+}  // namespace rom_test
+
+#endif  // OPENTITAN_SW_DEVICE_SILICON_CREATOR_LIB_DRIVERS_MOCK_IBEX_H_

sw/device/silicon_creator/lib/drivers/mock_ibex.h

@@ -10,8 +10,8 @@
 #include "sw/device/lib/base/csr.h"
 #include "sw/device/lib/base/mock_abs_mmio.h"
 #include "sw/device/lib/base/mock_crc32.h"
-#include "sw/device/silicon_creator/lib/base/mock_csr.h"
 #include "sw/device/silicon_creator/lib/base/mock_sec_mmio.h"
+#include "sw/device/silicon_creator/lib/drivers/mock_ibex.h"
 #include "sw/device/silicon_creator/lib/drivers/mock_otp.h"
 #include "sw/device/silicon_creator/testing/rom_test.h"
 
@@ -34,29 +34,23 @@ class RndTest : public rom_test::RomTest {
   rom_test::MockAbsMmio mmio_;
   rom_test::MockSecMmio sec_mmio_;
   rom_test::MockOtp otp_;
-  mock_csr::MockCsr csr_;
+  rom_test::MockIbex ibex_;
 };
 
 TEST_F(RndTest, GetUint32Enabled) {
   EXPECT_CALL(otp_, read32(OTP_CTRL_PARAM_CREATOR_SW_CFG_RNG_EN_OFFSET))
       .WillOnce(Return(kHardenedBoolTrue));
+  EXPECT_CALL(ibex_, Rnd32()).WillOnce(Return(12345));
 
-  EXPECT_ABS_READ32(base_rv_ + RV_CORE_IBEX_RND_STATUS_REG_OFFSET,
-                    {{RV_CORE_IBEX_RND_STATUS_RND_DATA_VALID_BIT, false}});
-  EXPECT_ABS_READ32(base_rv_ + RV_CORE_IBEX_RND_STATUS_REG_OFFSET,
-                    {{RV_CORE_IBEX_RND_STATUS_RND_DATA_VALID_BIT, true}});
-  EXPECT_CSR_READ(CSR_REG_MCYCLE, 67894);
-  EXPECT_ABS_READ32(base_rv_ + RV_CORE_IBEX_RND_DATA_REG_OFFSET, 12345);
-  EXPECT_EQ(rnd_uint32(), 67894 + 12345);
+  EXPECT_EQ(rnd_uint32(), 12345);
 }
 
 TEST_F(RndTest, GetUint32Disabled) {
   EXPECT_CALL(otp_, read32(OTP_CTRL_PARAM_CREATOR_SW_CFG_RNG_EN_OFFSET))
       .WillOnce(Return(kHardenedBoolFalse));
+  EXPECT_CALL(ibex_, MCycle32()).WillOnce(Return(978465));
 
-  EXPECT_CSR_READ(CSR_REG_MCYCLE, 978465);
-  EXPECT_ABS_READ32(base_rv_ + RV_CORE_IBEX_RND_DATA_REG_OFFSET, 193475837);
-  EXPECT_EQ(rnd_uint32(), 978465 + 193475837);
+  EXPECT_EQ(rnd_uint32(), 978465);
 }
 
 struct RndtLcStateTestCfg {