Change in coreboot[master]: console/flashsconsole: Adding a spi flash console for debugging

[Youness Alaoui (Code Review)]

Youness Alaoui has uploaded a new patch set (#2). ( https://review.coreboot.org/19849 )

Change subject: console/flashsconsole: Adding a spi flash console for debugging
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console/flashsconsole: Adding a spi flash console for debugging

If CONSOLE_SPI_FLASH config is enabled, we can write the cbmem
messages to the 'console' region in CBFS which allows
us to grab the log when we read the flash.

This is useful when you don't have usb debugging, and
UART lines are hard to find. Since a failure to boot would
require a hardware flasher anyways, we can get the log
at the same time.

This feature should only be used when no alternative is
found and only when we can't boot the system, because
excessive writes to the flash is not recommended.

This has been tested on purism/librem13 v2 and librem 15 v3 which
run skylake hardware. It has not been tested on other archs or with
a driver other than the fast_spi.

The Kconfig help mentions support for writing to an fmap area
but this isn't supported yet.

Change-Id: I74a297b94f6881d8c27cbe5168f161d8331c3df3
Signed-off-by: Youness Alaoui 
---
M src/console/Kconfig
M src/console/console.c
M src/drivers/spi/Makefile.inc
A src/drivers/spi/flashconsole.c
A src/include/console/flash.h
5 files changed, 254 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/49/19849/2