From c47fc4002261e241890c098335eaaf4cb51c844a Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Michael=20Niew=C3=B6hner?= Date: Sat, 25 Sep 2021 00:10:30 +0200 Subject: soc/intel/pmc: add a note about legacy OSes/payloads to PM Timer Kconfig MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Since ACPI 5.0A it is allowed to disable the ACPI Timer, when the according FADT flag `ACPI_FADT_PLATFORM_CLOCK` is unset. Starting with Skylake, most platforms (except Xeon-SP) support PM Timer emulation, so even legacy OSes and payloads should work fine with the hardware PM Timer disabled. However, when the `TMR_STS` functionality is required, some legacy OSes might still not work (properly). Add a note about this to the Kconfig help. Change-Id: I53f1814113902124779ed85da030374439570688 Signed-off-by: Michael Niewöhner Reviewed-on: https://review.coreboot.org/c/coreboot/+/58018 Tested-by: build bot (Jenkins) Reviewed-by: Nico Huber Reviewed-by: Lance Zhao --- src/soc/intel/common/block/pmc/Kconfig | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'src/soc/intel/common') diff --git a/src/soc/intel/common/block/pmc/Kconfig b/src/soc/intel/common/block/pmc/Kconfig index e3978e29dd..5e5e8d6184 100644 --- a/src/soc/intel/common/block/pmc/Kconfig +++ b/src/soc/intel/common/block/pmc/Kconfig @@ -76,4 +76,11 @@ config USE_PM_ACPI_TIMER Disabling this option also stops the hardware TCO timer and makes the TCO watchdog unavailable. + Note: On platforms without uCode PM Timer emulation, legacy OSes + or payloads with ACPI version < 5.0A might not work without + PM ACPI timer. + + (Legacy) software requiring `TMR_STS` (for timer overflow + interrupts) will not work with this option disabled. + endif # PM_ACPI_TIMER_OPTIONAL -- cgit v1.2.3