[entropy_src,sival] Implement entropy_src_fw_observe_many_contiguous

Signed-off-by: Amaury Pouly <[email protected]>
(cherry picked from commit 60a31ea)

Author: pamaury

hw/top_earlgrey/data/ip/chip_entropy_src_testplan.hjson

@@ -211,7 +211,7 @@
       si_stage: SV3
       lc_states: ["TEST_UNLOCKED", "PROD"]
       tests: []
-      bazel: []
+      bazel: ["//sw/device/tests:entropy_src_fw_observe_many_contiguous_test"]
     },
     {
       name: chip_sw_entropy_src_fw_extract_and_insert

sw/device/tests/BUILD

@@ -1302,6 +1302,30 @@ opentitan_test(
     ],
 )
 
+opentitan_test(
+    name = "entropy_src_fw_observe_many_contiguous_test",
+    srcs = ["entropy_src_fw_observe_many_contiguous.c"],
+    exec_env = dicts.add(
+        EARLGREY_TEST_ENVS,
+        EARLGREY_SILICON_OWNER_ROM_EXT_ENVS,
+        {
+            "//hw/top_earlgrey:silicon_creator": None,
+        },
+    ),
+    deps = [
+        "//hw/ip/entropy_src/data:entropy_src_regs",
+        "//hw/top_earlgrey/sw/autogen:top_earlgrey",
+        "//sw/device/lib/base:memory",
+        "//sw/device/lib/base:mmio",
+        "//sw/device/lib/dif:base",
+        "//sw/device/lib/dif:entropy_src",
+        "//sw/device/lib/runtime:log",
+        "//sw/device/lib/testing:edn_testutils",
+        "//sw/device/lib/testing:entropy_testutils",
+        "//sw/device/lib/testing/test_framework:ottf_main",
+    ],
+)
+
 opentitan_test(
     name = "entropy_src_edn_reqs_test",
     srcs = ["entropy_src_edn_reqs_test.c"],

sw/device/tests/entropy_src_fw_observe_many_contiguous.c

@@ -0,0 +1,228 @@
+// Copyright lowRISC contributors.
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "sw/device/lib/base/memory.h"
+#include "sw/device/lib/base/mmio.h"
+#include "sw/device/lib/dif/dif_base.h"
+#include "sw/device/lib/dif/dif_entropy_src.h"
+#include "sw/device/lib/runtime/log.h"
+#include "sw/device/lib/testing/edn_testutils.h"
+#include "sw/device/lib/testing/entropy_testutils.h"
+#include "sw/device/lib/testing/test_framework/check.h"
+#include "sw/device/lib/testing/test_framework/ottf_main.h"
+
+#include "entropy_src_regs.h"                         // Generated.
+#include "hw/top_earlgrey/sw/autogen/top_earlgrey.h"  // Generated.
+
+OTTF_DEFINE_TEST_CONFIG();
+
+enum {
+  kEntropySrcHealthTestWindowSize = 0x200,
+  /**
+   * Observe FIFO threshold: half of the FIFO size.
+   */
+  kEntropySrcFifoThreshold = 32,
+  /**
+   * The number of contiguous samples we want to capture.
+   */
+  kContiguousSamplesCount = 1024,
+  /*
+   * Timeout to read kContiguousSamplesCount.
+   */
+  kTimeoutUsec = 1000 * 1000,
+  /**
+   * Number of time to repeat each test, letting the observe FIFO
+   * overflow in-between tests.
+   */
+  kRepeatCount = 4,
+  /**
+   * Number of bits per sample.
+   */
+  kBitsPerSample = 4,
+  /**
+   * Size of buffer in words to hold all the samples, assuming
+   * 4-bit samples at the most.
+   */
+  kFifoBufferSizeWords =
+      kContiguousSamplesCount * kBitsPerSample / sizeof(uint32_t),
+};
+
+static uint32_t sample_buffer[kFifoBufferSizeWords];
+static dif_entropy_src_t entropy_src;
+static dif_csrng_t csrng;
+static dif_edn_t edn0;
+static dif_edn_t edn1;
+
+/**
+ * Determine whether the observe FIFO has overflowed.
+ *
+ * TODO(#21279) Normally, one would rely on the FW_OV_RD_FIFO_OVERFLOW
+ * register but due to an RTL bug, the overflow bit is pulsed
+ * instead of latched so we cannot rely on it. Instead, rely
+ * on OBSERVE_FIFO_DEPTH and assume that if the FIFO is full
+ * then it has overflowed.
+ */
+bool entropy_src_fifo_has_overflowed(void) {
+  uint32_t fifo_depth;
+  CHECK_DIF_OK(dif_entropy_src_get_fifo_depth(&entropy_src, &fifo_depth));
+  return fifo_depth == ENTROPY_SRC_PARAM_OBSERVE_FIFO_DEPTH;
+}
+
+/**
+ * Drain observe FIFO and clear overflow status if set.
+ */
+static void drain_observe_fifo(void) {
+  // This value is arbitrary, it could be 1 but since there is some
+  // overhead in dif_entropy_src_observe_fifo_nonblocking_read, it's better
+  // to read several words every time to drain the FIFO quickly.
+  const size_t kDrainCount = 32;
+  size_t len;
+  // Read from the FIFO until we get a short read which means that the FIFO was
+  // emptied.
+  LOG_INFO("drain observe FIFO overflow...");
+  do {
+    len = kDrainCount;
+    CHECK_DIF_OK(dif_entropy_src_observe_fifo_nonblocking_read(&entropy_src,
+                                                               NULL, &len));
+  } while (len == kDrainCount);
+  CHECK_DIF_OK(dif_entropy_src_clear_fifo_overflow(&entropy_src));
+}
+
+/**
+ * Let observe FIFO overflow.
+ */
+static status_t let_observe_fifo_overflow(uint32_t timeout_usec) {
+  LOG_INFO("let observe FIFO overflow...");
+  IBEX_TRY_SPIN_FOR(entropy_src_fifo_has_overflowed(), timeout_usec);
+  return OK_STATUS();
+}
+
+// Configure the entropy complex.
+static status_t entropy_config(
+    dif_entropy_src_single_bit_mode_t single_bit_mode) {
+  dif_edn_auto_params_t edn_params0 =
+      edn_testutils_auto_params_build(false, /*res_itval=*/0, /*glen_val=*/0);
+  dif_edn_auto_params_t edn_params1 =
+      edn_testutils_auto_params_build(false, /*res_itval=*/0, /*glen_val=*/0);
+  // Disable the entropy complex.
+  TRY(entropy_testutils_stop_all());
+
+  // Disable all health tests.
+  static dif_entropy_src_test_t kHealthTest[] = {
+      kDifEntropySrcTestRepetitionCount,
+      kDifEntropySrcTestRepetitionCountSymbol,
+      kDifEntropySrcTestAdaptiveProportion, kDifEntropySrcTestBucket,
+      kDifEntropySrcTestMarkov};
+  for (size_t i = 0; i < ARRAYSIZE(kHealthTest); i++) {
+    TRY(dif_entropy_src_health_test_configure(
+        &entropy_src,
+        (dif_entropy_src_health_test_config_t){.test_type = kHealthTest[i],
+                                               .high_threshold = 0xffffffff,
+                                               .low_threshold = 0}));
+  }
+  // Enable FW override.
+  TRY(dif_entropy_src_fw_override_configure(
+      &entropy_src,
+      (dif_entropy_src_fw_override_config_t){
+          .entropy_insert_enable = false,
+          .buffer_threshold = kEntropySrcFifoThreshold,
+      },
+      kDifToggleEnabled));
+  // Enable entropy_src.
+  TRY(dif_entropy_src_configure(
+      &entropy_src,
+      (dif_entropy_src_config_t){
+          .fips_enable = true,
+          .route_to_firmware = false,
+          .bypass_conditioner = false,
+          .single_bit_mode = single_bit_mode,
+          .health_test_threshold_scope = false,
+          .health_test_window_size = kEntropySrcHealthTestWindowSize,
+          .alert_threshold = UINT16_MAX},
+      kDifToggleEnabled));
+
+  // Enable CSRNG
+  TRY(dif_csrng_configure(&csrng));
+  // Enable EDNs in auto request mode
+  TRY(dif_edn_set_auto_mode(&edn0, edn_params0));
+  TRY(dif_edn_set_auto_mode(&edn1, edn_params1));
+  return OK_STATUS();
+}
+
+/**
+ * Test the firmware override observe path.
+ *
+ * @param entropy An Entropy handle.
+ */
+status_t firmware_override_observe(
+    uint32_t nr_samples, dif_entropy_src_single_bit_mode_t single_bit_mode,
+    uint32_t timeout_usec, uint32_t repeat_count) {
+  // Slow computation: do it once.
+  uint32_t nr_sample_words =
+      ceil_div(nr_samples * kBitsPerSample, sizeof(uint32_t));
+  // Configure the entropy complex.
+  entropy_config(single_bit_mode);
+
+  LOG_INFO("==================");
+  LOG_INFO("Running test in mode %u, will run test %u times", single_bit_mode,
+           repeat_count);
+  while (repeat_count-- > 0) {
+    LOG_INFO("collecting %u samples...", nr_samples);
+    // Collect samples from the the observe FIFO.
+    uint32_t words_to_read = nr_sample_words;
+    uint32_t *sample_buffer_ptr = sample_buffer;
+    // Drain FIFO to make sure we get contiguous samples.
+    drain_observe_fifo();
+    // Collect.
+    ibex_timeout_t tmo = ibex_timeout_init(timeout_usec);
+    while (words_to_read > 0 && !ibex_timeout_check(&tmo)) {
+      size_t len = words_to_read;
+      // Check FIFO did not overflow during collection.
+      TRY_CHECK(!entropy_src_fifo_has_overflowed(),
+                "observe FIFO overflowed during collection");
+      TRY(dif_entropy_src_observe_fifo_nonblocking_read(
+          &entropy_src, sample_buffer_ptr, &len));
+      sample_buffer_ptr += len;
+      words_to_read -= len;
+    }
+    TRY_CHECK(!ibex_timeout_check(&tmo), "did not collect samples in time");
+    // Make sure the FIFO did not overflow.
+    uint64_t elapsed = ibex_timeout_elapsed(&tmo);
+    uint64_t freq =
+        udiv64_slow((uint64_t)nr_samples * (uint64_t)1000000, elapsed, NULL);
+    LOG_INFO("done in %ums (~ %usamples/s)",
+             (uint32_t)udiv64_slow(elapsed, 1000, NULL), (uint32_t)freq);
+
+    // Let observe FIFO overflow
+    if (repeat_count > 0) {
+      TRY(let_observe_fifo_overflow(timeout_usec));
+    }
+  }
+  return OK_STATUS();
+}
+
+bool test_main(void) {
+  CHECK_DIF_OK(dif_entropy_src_init(
+      mmio_region_from_addr(TOP_EARLGREY_ENTROPY_SRC_BASE_ADDR), &entropy_src));
+  CHECK_DIF_OK(dif_csrng_init(
+      mmio_region_from_addr(TOP_EARLGREY_CSRNG_BASE_ADDR), &csrng));
+  CHECK_DIF_OK(
+      dif_edn_init(mmio_region_from_addr(TOP_EARLGREY_EDN0_BASE_ADDR), &edn0));
+  CHECK_DIF_OK(
+      dif_edn_init(mmio_region_from_addr(TOP_EARLGREY_EDN1_BASE_ADDR), &edn1));
+  // Test all modes.
+  static dif_entropy_src_single_bit_mode_t kModes[] = {
+      kDifEntropySrcSingleBitModeDisabled, kDifEntropySrcSingleBitMode0,
+      kDifEntropySrcSingleBitMode1,        kDifEntropySrcSingleBitMode2,
+      kDifEntropySrcSingleBitMode3,
+  };
+  status_t test_result = OK_STATUS();
+  for (size_t i = 0; i < ARRAYSIZE(kModes); i++) {
+    EXECUTE_TEST(test_result, firmware_override_observe,
+                 kContiguousSamplesCount, kModes[i], kTimeoutUsec,
+                 kRepeatCount);
+  }
+
+  return status_ok(test_result);
+}