xtensa/esp32: Fix himem driver crash in SMP mode

arch/xtensa/src/esp32/esp32_spiram.c

@@ -34,6 +34,7 @@
 #include <sys/param.h>
 #include <nuttx/config.h>
 #include <nuttx/spinlock.h>
+#include <nuttx/init.h>
 
 #include "esp32_spiram.h"
 #include "esp32_spicache.h"
@@ -85,7 +86,9 @@ unsigned int IRAM_ATTR cache_sram_mmu_set(int cpu_no, int pid,
   uint32_t regval;
   uint32_t statecpu0;
 #ifdef CONFIG_SMP
+  int cpu_to_stop = 0;
   uint32_t statecpu1;
+  bool smp_start = OSINIT_OS_READY();
 #endif
   unsigned int i;
   unsigned int shift;
@@ -168,14 +171,24 @@ unsigned int IRAM_ATTR cache_sram_mmu_set(int cpu_no, int pid,
    * the flash guards to make sure the cache is disabled.
    */
 
-  flags = spin_lock_irqsave(NULL);
+  flags = enter_critical_section();
-
-  spi_disable_cache(0, &statecpu0);
 
 #ifdef CONFIG_SMP
+  /* The other CPU might be accessing the cache at the same time, just by
+   * using variables in external RAM.
+   */
+
+  if (smp_start)
+    {
+      cpu_to_stop = up_cpu_index() == 1 ? 0 : 1;
+      up_cpu_pause(cpu_to_stop);
+    }
+
   spi_disable_cache(1, &statecpu1);
 #endif
 
+  spi_disable_cache(0, &statecpu0);
+
   /* mmu change */
 
   for (i = 0; i < num; i++)
@@ -203,9 +216,14 @@ unsigned int IRAM_ATTR cache_sram_mmu_set(int cpu_no, int pid,
   spi_enable_cache(0, statecpu0);
 #ifdef CONFIG_SMP
   spi_enable_cache(1, statecpu1);
+
+  if (smp_start)
+    {
+      up_cpu_resume(cpu_to_stop);
+    }
 #endif
 
-  spin_unlock_irqrestore(NULL, flags);
+  leave_critical_section(flags);
   return 0;
 }