soc/amd/common/psp_verstage: Map/unmap boot device on need basis

Currently the SPI ROM is mapped completely when the boot device is
initialized. That mapping remains active throughout the execution time
of PSP verstage. Every 1 MiB of mapped SPI ROM region consumes 1 TLB
Slot in PSP for use during memory mapped or DMA access. With 16 MiB of
mapped SPI ROM + FCH devices + 4 reserved TLB slots, 31 out of 32 total
TLB slots is consumed. This leaves almost no scope for future expansion.
With upcoming programs possibly using 32 MiB SPI ROM, PSP will run out
of TLB slots to support 32 MiB.

Hence instead of mapping the entire SPI ROM upfront, get the SPI ROM SMN
address during the boot device initialization. Update the boot device
region operations to map and unmap the SPI flash with the desired offset
and size using the SVC call. Then anytime a memory mapped SPI ROM access
is performed: map the required area, read the data and immediately unmap
the area. There is no update required when using CCP DMA, since the
concerned SVC call performs mapping and unmapping of the required SPI
flash area implicitly.

With these changes, maximum of 8 slots(size of RO section) might get
used at any point in time during the PSP verstage execution.

BUG=b:240664755
TEST=Build and boot to OS in Skyrim. Perform cold, warm reboots and
suspend/resume cycles for 50 iterations each. Ensured that there is no
impact to boot time.

Change-Id: Icd44ea7b2a366e9269debcab4186d1fc71651db2
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74606
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions