Consolidate reset API, add generic reset_prepare mechanism

There are many good reasons why we may want to run some sort of generic
callback before we're executing a reset. Unfortunateley, that is really
hard right now: code that wants to reset simply calls the hard_reset()
function (or one of its ill-differentiated cousins) which is directly
implemented by a myriad of different mainboards, northbridges, SoCs,
etc. More recent x86 SoCs have tried to solve the problem in their own
little corner of soc/intel/common, but it's really something that would
benefit all of coreboot.

This patch expands the concept onto all boards: hard_reset() and friends
get implemented in a generic location where they can run hooks before
calling the platform-specific implementation that is now called
do_hard_reset(). The existing Intel reset_prepare() gets generalized as
soc_reset_prepare() (and other hooks for arch, mainboard, etc. can now
easily be added later if necessary). We will also use this central point
to ensure all platforms flush their cache before reset, which is
generally useful for all cases where we're trying to persist information
in RAM across reboots (like the new persistent CBMEM console does).

Also remove cpu_reset() completely since it's not used anywhere and
doesn't seem very useful compared to the others.

Change-Id: I41b89ce4a923102f0748922496e1dd9bce8a610f
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/19789
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

1 files changed, 26 insertions, 11 deletions

diff --git a/src/include/reset.h b/src/include/reset.h
index f7501b53da..934ed9b1fc 100644
--- a/src/include/reset.h
+++ b/src/include/reset.h
@@ -1,15 +1,30 @@
 #ifndef RESET_H
 #define RESET_H
 
-#if CONFIG_HAVE_HARD_RESET
-void hard_reset(void);
-#else
-#define hard_reset() do {} while (0)
-#endif
-void soft_reset(void);
-void cpu_reset(void);
-/* Some Intel SoCs use a special reset that is specific to SoC */
-void global_reset(void);
-/* Some Intel SoCs may need to prepare/wait before reset */
-void reset_prepare(void);
+/* Generic reset functions. Call from code that wants to trigger a reset. */
+
+/* Super-hard reset specific to some Intel SoCs. */
+__attribute__((noreturn)) void global_reset(void);
+/* Full board reset. Resets SoC and most/all board components (e.g. DRAM). */
+__attribute__((noreturn)) void hard_reset(void);
+/* Board reset. Resets SoC some board components (e.g. TPM but not DRAM). */
+__attribute__((noreturn)) void soft_reset(void);
+
+/* Reset implementations. Implement these in SoC or mainboard code. Implement
+   at least hard_reset() if possible, others fall back to it if necessary. */
+void do_global_reset(void);
+void do_hard_reset(void);
+void do_soft_reset(void);
+
+enum reset_type {	/* listed in order of softness */
+	GLOBAL_RESET,
+	HARD_RESET,
+	SOFT_RESET,
+};
+
+/* Callback that an SoC may override to perform special actions before reset.
+   Take into account that softer resets may fall back to harder resets if not
+   implemented... this will *not* trigger another callback! */
+void soc_reset_prepare(enum reset_type reset_type);
+
 #endif