soc/amd/common/block: Add spi_hw mutex

There are currently two users of the SPI hardware, the LPC SPI DMA
controller, and the boot_device_rw device. We need to ensure exclusivity
to the SPI hardware otherwise the SPI DMA controller can be interrupted
and it will silently skip transferring some blocks.

Depending on the SPI speed, this change might add a small delay when
clearing the elog since a DMA transaction might be in flight. I'll
continue optimizing the boot flow to avoid the delay.

BUG=b:179699789
TEST=Hack up the code to interleave SPI transactions and verify this
patch fixes the silent data corruption.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: I5eee812a6979c8c0fb313dd2fbccc14b73d7d741
Reviewed-on: https://review.coreboot.org/c/coreboot/+/58926
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

0 files changed, 0 insertions, 0 deletions