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| author | Tim Wawrzynczak <twawrzynczak@chromium.org> | 2020-05-20 10:05:08 -0600 |
|---|---|---|
| committer | Tim Wawrzynczak <twawrzynczak@chromium.org> | 2020-06-06 01:33:38 +0000 |
| commit | a4e2e0550cef1b8a888ec75653c96ac070fca825 (patch) | |
| tree | a1b6c0a4046ca78e97304c290aa997c1a243ce68 /Documentation/releases | |
| parent | 554b03038e487c4ca8347688d8641a6c132e4b9b (diff) | |
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 <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41563
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Diffstat (limited to 'Documentation/releases')
| -rw-r--r-- | Documentation/releases/coreboot-4.13-relnotes.md | 15 |
1 files changed, 15 insertions, 0 deletions
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 |