console/flashsconsole: Add spi flash console for debugging

If CONSOLE_SPI_FLASH config is enabled, we write the cbmem
messages to the 'CONSOLE' area in FMAP 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 Intel Skylake hardware. It has not been tested on other archs
or with a driver other than the fast_spi.

Change-Id: I74a297b94f6881d8c27cbe5168f161d8331c3df3
Signed-off-by: Youness Alaoui <youness.alaoui@puri.sm>
Reviewed-on: https://review.coreboot.org/19849
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>

2 files changed, 35 insertions, 0 deletions

diff --git a/src/console/Kconfig b/src/console/Kconfig
index caf91ab252..c0e4a8c8b0 100644
--- a/src/console/Kconfig
+++ b/src/console/Kconfig
@@ -233,6 +233,37 @@ config CONSOLE_CBMEM_DUMP_TO_UART
 
 endif
 
+config CONSOLE_SPI_FLASH
+	bool "SPI Flash console output"
+	default n
+	select BOOT_DEVICE_SPI_FLASH_RW_NOMMAP_EARLY if !COMMON_CBFS_SPI_WRAPPER
+	help
+	  Send coreboot debug output to the SPI Flash in the FMAP CONSOLE area
+
+	  This option can cause premature wear on the SPI flash and should not
+	  be used as a normal means of debugging. It is only to be enabled and
+	  used when porting a new motherboard which has no other console
+	  available (no UART, no POST, no cbmem access(non bootable)). Since
+	  a non bootable machine will require the use of an external SPI Flash
+	  programmer, the developer can grab the console log at the same time.
+
+	  The flash console will not be erased on reboot, so once it is full,
+	  the flashconsole driver will stop writing to it. This is to avoid
+	  wear on the flash, and to avoid erasing sectors (which may freeze
+	  the SPI controller on skylake).
+
+	  The 'CONSOLE' area can be extracted from the FMAP with :
+	  cbfstool rom.bin read -r CONSOLE -f console.log
+
+config CONSOLE_SPI_FLASH_BUFFER_SIZE
+	hex "Room allocated for console output in FMAP"
+	default 0x20000
+	depends on CONSOLE_SPI_FLASH
+	help
+	  Space allocated for console output storage in FMAP. The default
+	  value (128K or 0x20000 bytes) is large enough to accommodate
+	  even the BIOS_SPEW level.
+
 config CONSOLE_QEMU_DEBUGCON
 	bool "QEMU debug console output"
 	depends on BOARD_EMULATION_QEMU_X86
diff --git a/src/console/console.c b/src/console/console.c
index 7b0dfc2fb1..877c8dc960 100644
--- a/src/console/console.c
+++ b/src/console/console.c
@@ -21,6 +21,7 @@
 #include <console/uart.h>
 #include <console/usb.h>
 #include <console/spi.h>
+#include <console/flash.h>
 #include <rules.h>
 
 void console_hw_init(void)
@@ -33,6 +34,7 @@ void console_hw_init(void)
 	__ne2k_init();
 	__usbdebug_init();
 	__spiconsole_init();
+	__flashconsole_init();
 }
 
 void console_tx_byte(unsigned char byte)
@@ -53,6 +55,7 @@ void console_tx_byte(unsigned char byte)
 	__ne2k_tx_byte(byte);
 	__usb_tx_byte(byte);
 	__spiconsole_tx_byte(byte);
+	__flashconsole_tx_byte(byte);
 }
 
 void console_tx_flush(void)
@@ -60,6 +63,7 @@ void console_tx_flush(void)
 	__uart_tx_flush();
 	__ne2k_tx_flush();
 	__usb_tx_flush();
+	__flashconsole_tx_flush();
 }
 
 void console_write_line(uint8_t *buffer, size_t number_of_bytes)