reset: Provide new single-function reset API

board_reset() replaces the existing common reset API. There is no common
distinction between reset types across platforms, hence, common code
could never decide which one to call.

Currently only hard_reset() is used by common code. We replace these
calls and provide a fall-back to the current hard_reset() implemen-
tation. The fall-back will be removed along with hard_reset() after the
transition of all boards.

Change-Id: I274a8cee9cb38226b5a0bdff6a847c74ef0b3128
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/29047
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/reset.h

@@ -1,7 +1,43 @@
 #ifndef RESET_H
 #define RESET_H
 
-/* Generic reset functions. Call from code that wants to trigger a reset. */
+/*
+ * Generic board reset function. Call from common code that
+ * wants to trigger a reset.
+ */
+__noreturn void board_reset(void);
+/*
+ * SoC or board specific implementation of the board reset.
+ *
+ * Implementations shall meet the following criteria:
+ *
+ *   o For vboot support, the TPM MUST be reset.
+ *
+ *   o All SoC/chipset blocks SHOULD be reset except for those
+ *     that are intentionally meant to survive reset (e.g. tomb-
+ *     stone registers and that sort of stuff).
+ *
+ *   o All external SoC pins SHOULD return to power-on reset values.
+ *
+ *   o The CPU MUST resume execution from power-on reset vector
+ *     (same as cold boot).
+ *
+ *   o Other board components (e.g. PCI, SDIO and stuff) SHOULD
+ *     be reset.
+ *
+ *   o USB SHOULD be power-cycled.
+ *
+ *   o Board components that are intended to be fully independent
+ *     from SoC (e.g. EC and EC-attached devices, the Cr50 on
+ *     Chromebooks) SHOULD NOT be reset.
+ *
+ * General recommendations:
+ *
+ *   o DRAM SHOULD NOT lose power if possible.
+ *
+ *   o Reset time SHOULD be minimized
+ */
+void do_board_reset(void);
 
 /* Super-hard reset specific to some Intel SoCs. */
 __noreturn void global_reset(void);