sdm845: Implement bitbang UART for bootblock

This patch replaces the UART in the bootblock of SDM845 with a bitbang
implementation. Since SDM845 hardware UART needs a firmware blob loaded
into it before it becomes usable, it is not really suited for use in the
bootblock (since by the time we can read blobs from SPI, the bootblock
is essentially over anyway). This solution allows us to still have some
console output during early SoC initialization.

Change-Id: I0c252ec83a7993edce5c4debc687f1fdd0d7b36d
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/25813
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/soc/qualcomm/sdm845/Makefile.inc b/src/soc/qualcomm/sdm845/Makefile.inc
index 1fddb56345..e603177317 100644
--- a/src/soc/qualcomm/sdm845/Makefile.inc
+++ b/src/soc/qualcomm/sdm845/Makefile.inc
@@ -7,6 +7,7 @@ bootblock-y += spi.c
 bootblock-y += mmu.c
 bootblock-y += timer.c
 bootblock-y += gpio.c
+bootblock-$(CONFIG_DRIVERS_UART) += uart_bitbang.c
 
 ################################################################################
 verstage-y += spi.c