soc/amd/common/blk/pcie: Program LTR max latencies

PCIe bridges need to provide the LTR (latency tolerance reporting)
maximum snoop/non-snoop values so that they are inherited by downstream
PCIe devices which support and enable LTR. Without this, downstream
devices cannot have LTR enabled, which is a requirement for supporting
PCIe L1 substates. Enabling L1ss without LTR has unpredictable behavior,
including some devices refusing to enter L1 low power modes at all.

Program the max snoop/non-snoop latency values for all PCIe bridges
using the same value used by AGESA/FSP, 1.049ms.

BUG=b:265890321
TEST=build/boot google/skyrim (multiple variants, NVMe drives), ensure
LTR is enabled, latency values are correctly set, and that device
power draw at idle is in the expected range (<25 mW).

Change-Id: Icf188e69cf5676be870873c56d175423d16704b4
Signed-off-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/74288
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>

0 files changed, 0 insertions, 0 deletions