From a4e2e0550cef1b8a888ec75653c96ac070fca825 Mon Sep 17 00:00:00 2001 From: Tim Wawrzynczak Date: Wed, 20 May 2020 10:05:08 -0600 Subject: Documentation: Add section about 'hidden' devices to 4.13 release notes CB:41384 (SHA dbcf7b16219df0c04401b8fcd6a780174a7df305) added some new functionality to devicetree files ("hidden PCI devices"). It's a decent enough semantic change that it should be added to the release notes for the 4.13 release. Change-Id: I52969f63dbc492afd32279176cbcfc2b76d7ac33 Signed-off-by: Tim Wawrzynczak Reviewed-on: https://review.coreboot.org/c/coreboot/+/41563 Tested-by: build bot (Jenkins) Reviewed-by: Furquan Shaikh Reviewed-by: Angel Pons --- Documentation/releases/coreboot-4.13-relnotes.md | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'Documentation') diff --git a/Documentation/releases/coreboot-4.13-relnotes.md b/Documentation/releases/coreboot-4.13-relnotes.md index 94e93bb75b..1d8839fea2 100644 --- a/Documentation/releases/coreboot-4.13-relnotes.md +++ b/Documentation/releases/coreboot-4.13-relnotes.md @@ -13,4 +13,19 @@ Update this document with changes that should be in the release notes. Significant changes ------------------- +### Hidden PCI devices + +This new functionality takes advantage of the existing 'hidden' keyword in the +devicetree. Since no existing boards were using the keyword, its usage was +repurposed to make dealing with some unique PCI devices easier. The particular +case here is Intel's PMC (Power Management Controller). During the FSP-S run, +the PMC device is made hidden, meaning that its config space looks as if there +is no device there (Vendor ID reads as 0xFFFF_FFFF). However, the device does +have fixed resources, both MMIO and I/O. These were previously recorded in +different places (MMIO was typically an SA fixed resource, and I/O was treated +as an LPC resource). With this change, when a device in the tree is marked as +'hidden', it is not probed (`pci_probe_dev()`) but rather assumed to exist so +that its resources can be placed in a more natural location. This also adds the +ability for the device to participate in SSDT generation. + ### Add significant changes here -- cgit v1.2.3