console: Implement pre-console buffer

Allow redirection of console output prior to console initialisation to a
temporary buffer.

To enable this functionality, the board (or arch) must define:
 - CONFIG_PRE_CONSOLE_BUFFER - Enable pre-console buffer
 - CONFIG_PRE_CON_BUF_ADDR - Base address of pre-console buffer
 - CONFIG_PRE_CON_BUF_SZ - Size of pre-console buffer (in bytes)

The pre-console buffer will buffer the last CONFIG_PRE_CON_BUF_SZ bytes
Any earlier characters are silently dropped.

Signed-off-by: Graeme Russ <graeme.russ@gmail.com>
Change-Id: I3c4caad276b9e981ebea0a0fb79d85ee3a3bcb7d
Reviewed-on: http://gerrit.chromium.org/gerrit/8686
Reviewed-by: Che-Liang Chiou <clchiou@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>

0 files changed, 0 insertions, 0 deletions