bootloader: add xmc spi_flash startup flow to improve reliability

components/bootloader_support/include/bootloader_flash.h

@@ -13,11 +13,24 @@
 // limitations under the License.
 #pragma once
 
+#include <stdint.h>
 #include <esp_err.h>
 #include <esp_spi_flash.h> /* including in bootloader for error values */
 #include "sdkconfig.h"
 #include "soc/soc_caps.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Read flash ID by sending 0x9F command
+ * @return flash raw ID
+ *     mfg_id = (ID >> 16) & 0xFF;
+       flash_id = ID & 0xffff;
+ */
+uint32_t bootloader_read_flash_id(void);
+
 #if SOC_CACHE_SUPPORT_WRAP
 /**
  * @brief Set the burst mode setting command for specified wrap mode.
@@ -28,3 +41,13 @@
 esp_err_t bootloader_flash_wrap_set(spi_flash_wrap_mode_t mode);
 #endif
 
+/**
+ * @brief Startup flow recommended by XMC. Call at startup before any erase/write operation.
+ *
+ * @return ESP_OK When startup successfully, otherwise ESP_FAIL (indiciating you should reboot before erase/write).
+ */
+esp_err_t bootloader_flash_xmc_startup(void);
+
+#ifdef __cplusplus
+}
+#endif