fix(spi_flash): disable branch prediction on the parked core during flash ops

components/esp_system/port/arch/riscv/esp_ipc_isr_routines.c

@@ -5,9 +5,21 @@
  */
 
 #include "stdint.h"
+#include "soc/soc_caps.h"
 #include "esp_attr.h"
+#include "esp_cpu.h"
 
 void IRAM_ATTR esp_ipc_isr_waiting_for_finish_cmd(void* ipc_isr_finish_cmd)
 {
+#if SOC_BRANCH_PREDICTOR_SUPPORTED
+    /* The branch predictor keeps issuing speculative instruction fetches while
+     * this core spins here. The other core may suspend the external memory
+     * cache during the stall, in which case a speculative fetch into cached
+     * address space raises a cache access-fail interrupt. */
+    esp_cpu_branch_prediction_disable();
+#endif
     while (*(volatile uint32_t *)ipc_isr_finish_cmd == 0) { };
+#if SOC_BRANCH_PREDICTOR_SUPPORTED
+    esp_cpu_branch_prediction_enable();
+#endif
 }

components/esp_system/port/panic_handler.c

@@ -130,6 +130,15 @@ static void frame_to_panic_info(void *frame, panic_info_t *info, bool pseudo_exc
 FORCE_INLINE_ATTR __attribute__((__noreturn__))
 void busy_wait(void)
 {
+#if SOC_BRANCH_PREDICTOR_SUPPORTED
+    /* This core parks here while the offending core handles the panic, which
+     * may include flash accesses with the cache suspended (e.g. writing a core
+     * dump). Stop the branch predictor so its speculative fetches cannot latch
+     * spurious cache access-fail errors that would corrupt the cache error
+     * status of the panic being reported. This core never resumes, so the
+     * predictor is not re-enabled. */
+    esp_cpu_branch_prediction_disable();
+#endif
     ESP_INFINITE_LOOP();
 }
 #endif // !CONFIG_ESP_SYSTEM_SINGLE_CORE_MODE

components/spi_flash/cache_utils.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2015-2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2015-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -126,6 +126,13 @@ void IRAM_ATTR spi_flash_op_block_func(void *arg)
     // Restore interrupts that aren't located in IRAM
     esp_intr_noniram_disable();
     uint32_t cpuid = (uint32_t) arg;
+#if SOC_BRANCH_PREDICTOR_SUPPORTED
+    /* The branch predictor issues speculative cache requests while this core
+     * spins in IRAM. The flash-op core is about to suspend the (shared) cache,
+     * so speculative fetches into flash would raise a cache access-fail on
+     * this core. spi_flash_restore_cache() below re-enables prediction. */
+    esp_cpu_branch_prediction_disable();
+#endif
     // s_flash_op_complete flag is cleared on *this* CPU, otherwise the other
     // CPU may reset the flag back to false before IPC task has a chance to check it
     // (if it is preempted by an ISR taking non-trivial amount of time)