From 64117a0c5932ec8138bfd702fa2f202df732bc71 Mon Sep 17 00:00:00 2001
From: Darian Leung <darian@espressif.com>
Date: Thu, 21 Jul 2022 19:14:10 +0800
Subject: [PATCH] esp_system: Fix esp_cpu_compare_and_set()

This commit fixes esp_cpu_compare_and_set() in the following ways

- Removed call to esp_ptr_external_ram() as it incurred > 80 CPU cycles (due to multiple nested
  function calls, and those functions not being in IRAM). We now check manually if the pointer
  is in external RAM for increased speed.
- Fixed infinite wait when attempting to get the external_ram_cas_lock. The function should
  return immediatley if any part of the compare and set call fails.
- The preprocessor conditions of esp_cpu_compare_and_set() to depend on CONFIG_SPIRAM instead
  of SOC_SPIRAM_SUPPORTED. Even if the target supports SPIRAM, we only need the external RAM
  compare and set feature if SPIRAM is enabled.

Also fixed incorrect inclusion of esp_intr_alloc.h in esp_cpu.h
---
 components/esp_hw_support/cpu.c             | 32 ++++++++++++---------
 components/esp_hw_support/include/esp_cpu.h |  1 +
 2 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/components/esp_hw_support/cpu.c b/components/esp_hw_support/cpu.c
index 163755b86d..6292cc22d4 100644
--- a/components/esp_hw_support/cpu.c
+++ b/components/esp_hw_support/cpu.c
@@ -620,7 +620,7 @@ esp_err_t esp_cpu_clear_watchpoint(int wp_num)
  *
  * ------------------------------------------------------------------------------------------------------------------ */
 
-#if __XTENSA__ && XCHAL_HAVE_S32C1I && SOC_SPIRAM_SUPPORTED
+#if __XTENSA__ && XCHAL_HAVE_S32C1I && CONFIG_SPIRAM
 static DRAM_ATTR uint32_t external_ram_cas_lock = 0;
 #endif
 
@@ -628,35 +628,39 @@ bool esp_cpu_compare_and_set(volatile uint32_t *addr, uint32_t compare_value, ui
 {
 #if __XTENSA__
     bool ret;
-#if XCHAL_HAVE_S32C1I && SOC_SPIRAM_SUPPORTED
-    if (esp_ptr_external_ram((const void *)addr)) {
+#if XCHAL_HAVE_S32C1I && CONFIG_SPIRAM
+    // Check if the target address is in external RAM
+    if ((uint32_t)addr >= SOC_EXTRAM_DATA_LOW && (uint32_t)addr < SOC_EXTRAM_DATA_HIGH) {
+        /* The target address is in external RAM, thus the native CAS instruction cannot be used. Instead, we achieve
+        atomicity by disabling interrupts and then acquiring an external RAM CAS lock. */
         uint32_t intr_level;
-        // Atomicity is achieved by disabling interrupts then acquiring a an external RAM CAS lock
         __asm__ __volatile__ ("rsil %0, " XTSTR(XCHAL_EXCM_LEVEL) "\n"
                               : "=r"(intr_level));
-        while (!xt_utils_compare_and_set(&external_ram_cas_lock, 0, 1)) {
-            ;
+        if (!xt_utils_compare_and_set(&external_ram_cas_lock, 0, 1)) {
+            // External RAM CAS lock already taken. Exit
+            ret = false;
+            goto exit;
         }
         // Now we compare and set the target address
-        uint32_t old_value;
-        old_value = *addr;
-        if (old_value == compare_value) {
+        ret = (*addr == compare_value);
+        if (ret) {
             *addr = new_value;
         }
-        // Release the external RAM CAS lock and reenable interrupts
+        // Release the external RAM CAS lock
         external_ram_cas_lock = 0;
+exit:
+        // Reenable interrupts
         __asm__ __volatile__ ("memw \n"
                               "wsr %0, ps\n"
                               :: "r"(intr_level));
-
-        ret = (old_value == compare_value);
     } else
-#endif  //XCHAL_HAVE_S32C1I && SOC_SPIRAM_SUPPORTED
+#endif  // XCHAL_HAVE_S32C1I && CONFIG_SPIRAM
     {
+        // The target address is in internal RAM. Use the CPU's native CAS instruction
         ret = xt_utils_compare_and_set(addr, compare_value, new_value);
     }
     return ret;
-#else
+#else // __XTENSA__
     // Single core targets don't have atomic CAS instruction. So access method is the same for internal and external RAM
     return rv_utils_compare_and_set(addr, compare_value, new_value);
 #endif
diff --git a/components/esp_hw_support/include/esp_cpu.h b/components/esp_hw_support/include/esp_cpu.h
index c4d74d93e8..2da71d54cc 100644
--- a/components/esp_hw_support/include/esp_cpu.h
+++ b/components/esp_hw_support/include/esp_cpu.h
@@ -17,6 +17,7 @@
 #elif __riscv
 #include "riscv/rv_utils.h"
 #endif
+#include "esp_intr_alloc.h"
 #include "esp_err.h"
 
 #ifdef __cplusplus