panic: Provide declarations for chip panic data backup/restore

Provide APIs that allow chips to implement their own version of
backing up/restoring panic data to persistent storage.

BUG=b:62076222
BRANCH=None
TEST=make -j buildall

Change-Id: Idda2d55703d4fe7e0a8d6305695fbf4e193b596b
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/530196
Reviewed-by: Mulin Chao <mlchao@nuvoton.com>
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>

include/config.h

@@ -745,6 +745,15 @@
  */
 #undef CONFIG_SOFTWARE_PANIC
 
+/*
+ * Certain platforms(e.g. eve, poppy) cannot retain panic info in data ram since
+ * VCC is powered down on EC reset. On such platforms, panic data needs to be
+ * saved/restored to persistent storage by using chip specific
+ * implementations. This option can be enabled by those platforms that have and
+ * wish to use chip-implemented panic backup/restore functions.
+ */
+#undef CONFIG_CHIP_PANIC_BACKUP
+
 /*
  * Provide the default GPIO abstraction layer.
  * You want this unless you are doing a really tiny firmware.

include/panic.h

@@ -170,4 +170,14 @@ void ignore_bus_fault(int ignored);
  */
 struct panic_data *panic_get_data(void);
 
+/**
+ * Chip-specific implementation for backing up panic data to persistent
+ * storage. This function is used to ensure that the panic data can survive loss
+ * of VCC power rail.
+ *
+ * There is no generic restore function provided since every chip can decide
+ * when it is safe to restore panic data during the system initialization step.
+ */
+void chip_panic_data_backup(void);
+
 #endif  /* __CROS_EC_PANIC_H */