Add spinlock synchronization to prevent concurrent SPI flash controller
access from multiple CPUs in SMP environments. The spinlock serializes
access to the SPI controller hardware in exec_sync_hwseq_xfer().
If SMP is not enabled, spinlock functions are no-ops, so this change
is safe for both SMP and non-SMP configurations.
This resolves an issue seen on the Starlabs Starfighter MTL where
multiple SPI transaction errors occurred when reading option variables
stored in SMMSTORE:
[ERROR] SPI Transaction Error at Flash Offset 103002a HSFSTS = 0x01016022
[ERROR] SPI Transaction Error at Flash Offset 1030004 HSFSTS = 0x01006022
[ERROR] SPI Transaction Error at Flash Offset 1030000 HSFSTS = 0x3f006022
...
Change-Id: Ic3003b0a986b587622102b6f36714bcb16c3d976
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90283
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
5034f8629f