timestamp: add generic cache region

In order to accommodate tracking timestamps in all the
__PRE_RAM__ stages (bootblock, verstage, romstage, etc)
of a platform one needs to provide a way to specify
a persistent region of SRAM or cache-as-ram to store
the timestamps until cbmem comes online. Provide that
infrastructure.

Based on original patches from chromium.org:
Original-Change-Id: I4d78653c0595523eeeb02115423e7fecceea5e1e
Original-Signed-off-by: Furquan Shaikh <furquan@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/223348
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>

Original-Change-Id: Ie5ffda3112d626068bd1904afcc5a09bc4916d16
Original-Signed-off-by: Furquan Shaikh <furquan@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/224024
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>
Original-Tested-by: Furquan Shaikh <furquan@chromium.org>

Change-Id: I8779526136e89ae61a6f177ce5c74a6530469ae1
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/10790
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)

1 files changed, 13 insertions, 0 deletions

diff --git a/src/include/timestamp.h b/src/include/timestamp.h
index a248ea45cd..54d69ce132 100644
--- a/src/include/timestamp.h
+++ b/src/include/timestamp.h
@@ -89,8 +89,21 @@ enum timestamp_id {
 };
 
 #if CONFIG_COLLECT_TIMESTAMPS && (CONFIG_EARLY_CBMEM_INIT || !defined(__PRE_RAM__))
+/*
+ * timestamp_init() needs to be called once for each of these cases:
+ *    1. __PRE_RAM__ (bootblock, romstage, verstage, etc) and
+ *    2. !__PRE_RAM__ (ramstage)
+ * The latter is taken care of by the generic coreboot infrastructure so
+ * it's up to the chipset/arch to call timestamp_init() in *one* of
+ * the __PRE_RAM__ stages. If multiple calls are made timestamps will be lost.
+ */
 void timestamp_init(uint64_t base);
+/*
+ * Add a new timestamp. Depending on cbmem is available or not, this timestamp
+ * will be stored to cbmem / timestamp cache.
+ */
 void timestamp_add(enum timestamp_id id, uint64_t ts_time);
+/* Calls timestamp_add with current timestamp. */
 void timestamp_add_now(enum timestamp_id id);
 #else
 #define timestamp_init(base)