common: add flash event log facility

This patch adds implementation and test for a generic logger saving
log entries in the flash.

The entries payload are limited to 64 bytes in size, each entry starts
with a header, which includes
 - 8 bit type type to allow to interpret the payload
 - 6 bit size field (two top bits of the byte are left for user flags,
   not yet used)
 - 32 bit timestamp to allow to identify newer log entries (presently
   this is just a monotonically increasing number)
 - 8 bit crc field protecting the entire entry

The entries are padded to make sure that they are ending on the flash
write boundary.

The location of the log is defined by the platform using it. There is
a provision for allowing the platform to register a callback which is
needed to be called to allow write access to the log (as is the case
on H1).

While the device is running, the log is growing until the allotted
flash space is 90% full. If there is an attempt save another entry
after that the log is compacted, namely the last 25% worth of flash
space is preserved, the log space is erased and the saved contents
written back.

On restarts the log is compacted if its size exceeds 75% of the
allotted flash space.

An API is provided to add entries to the log and to retrieve an entry
newer than a certain timestamp value. Thus starting with timestamp
zero will result in reading the very first log entry. To read the next
entry, the read function needs to be called with the timestamp value
of the current entry. This allows to browse the entire log, one entry
at a time.

A CLI command compiled in when CONFIG_CMD_FLASH_LOG is defined, allows
to add log and retrieve log entries.

BUG=b:63760920
BRANCH=cr50, cr50-mp
TEST=the included test case can be invoked by

     make run-flash_log

   and it passes. More tests are done when the rest of the patch stack
   is added.

Change-Id: I3dcdf2704a1e08fd3101183e434ac4a4e4cf1b9a
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1525143
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Andrey Pronin <apronin@chromium.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/chip/g/config_chip.h b/chip/g/config_chip.h
index a79ecf2ee0..365154fd5b 100644
--- a/chip/g/config_chip.h
+++ b/chip/g/config_chip.h
@@ -28,6 +28,7 @@
 /* Describe the flash layout */
 #define CONFIG_PROGRAM_MEMORY_BASE     0x40000
 #define CONFIG_FLASH_SIZE              (512 * 1024)
+#define CONFIG_FLASH_ERASED_VALUE32    (-1U)
 #define CONFIG_RO_HEAD_ROOM	       1024	/* Room for ROM signature. */
 #define CONFIG_RW_HEAD_ROOM	       CONFIG_RO_HEAD_ROOM  /* same for RW */