Merge 86b2700eb0 into c0e0af03d1

Mapping and unmapping is expensive so we map the entire partition and keep it mapped
anticipating that it will be reused. We only keep one partition mapped so alternating
reads between encrypted partitions will incur a penalty but hopefully that is uncommon.

components/spi_flash/partition.c

@@ -430,19 +430,32 @@ esp_err_t esp_partition_read(const esp_partition_t* partition,
         if (partition->flash_chip != esp_flash_default_chip) {
             return ESP_ERR_NOT_SUPPORTED;
         }
-
-        /* Encrypted partitions need to be read via a cache mapping */
-        const void *buf;
-        spi_flash_mmap_handle_t handle;
-        esp_err_t err;
-
-        err = esp_partition_mmap(partition, src_offset, size,
-                                 SPI_FLASH_MMAP_DATA, &buf, &handle);
-        if (err != ESP_OK) {
-            return err;
+        /*
+         * Encrypted partitions need to be read via a cache mapping.
+         * Mapping and unmapping is expensive so we map the entire partition and keep it mapped
+         * anticipating that it will be reused. We only keep one partition mapped so alternating
+         * reads between encrypted partitions will incur a penalty but hopefully that is uncommon.
+         */
+        static uint32_t s_mapped_partition_end = 0;
+        static const void *s_mapped_vaddr = NULL;
+        static spi_flash_mmap_handle_t s_map_handle = 0;
+        /* Since partitions are non-overlapping, addr + size uniquely identifies a partition. */
+        const uint32_t partition_end = partition->address + partition->size;
+        if (s_mapped_partition_end != partition_end) {
+            if (s_mapped_vaddr != NULL) {
+                spi_flash_munmap(s_map_handle);
+                s_mapped_partition_end = 0;
+                s_mapped_vaddr = NULL;
+                s_map_handle = 0;
+            }
+            esp_err_t err = esp_partition_mmap(
+                partition, 0, partition->size, SPI_FLASH_MMAP_DATA, &s_mapped_vaddr, &s_map_handle);
+            if (err != ESP_OK) {
+                return err;
+            }
+            s_mapped_partition_end = partition_end;
         }
-        memcpy(dst, buf, size);
-        spi_flash_munmap(handle);
+        memcpy(dst, ((const char *) s_mapped_vaddr) + src_offset, size);
         return ESP_OK;
 #else
         return ESP_ERR_NOT_SUPPORTED;