From: Lv Zheng lv.zheng@intel.com
[ Upstream commit c712bb58d8278465b1a91f362a08f5c79ad077e4 ]
We prepared _INI/_STA methods for _SB, _SB.PCI0, _SB.LID0 and _SB.EC, _HID(PNP0C09)/_CRS/_GPE for _SB.EC to poke Windows behavior with qemu, we got the following execution sequence:
_SB._INI _SB.PCI0._STA _SB.LID0._STA _SB.EC._STA _SB.PCI0._INI _SB.LID0._INI _SB.EC._INI
There is no extra DSDT EC device enumeration process occurring before the main ACPI device enumeration process. That means acpi_ec_dsdt_probe() is not Windows-compatible.
Tracking back, it was added by the following commit:
Commit: c5279dee26c0e8d7c4200993bfc4b540d2469598 Subject: ACPI: EC: Add some basic check for ECDT data
but that commit was misguided.
Why we shouldn't enumerate DSDT EC before the main ACPI device enumeration?
The only way to know if the DSDT EC is valid would be to evaluate its _STA control method, but it's not safe to evaluate this control method that early and out of the ACPI enumeration process, because _STA may refer to entities (such as resources or ACPI device objects) that may not have been initialized before OSPM starts to enumerate them via the main ACPI device enumeration.
But after we had reverted back to the expected behavior, a regression was reported. On that platform, there is no ECDT, but the platform control methods access EC operation region earlier than Linux expects causing some ACPI method execution errors. For this reason, we just go back to old behavior to still probe DSDT EC as the boot EC.
However, that turns out to lead to yet another functional breakage and in order to work around all of the problems, we skip boot stage DSDT probe when the ECDT exists so that a later quirk can always use correct ECDT GPE setting.
Link: http://bugzilla.kernel.org/show_bug.cgi?id=11880 Link: http://bugzilla.kernel.org/show_bug.cgi?id=119261 Link: http://bugzilla.kernel.org/show_bug.cgi?id=195651 Tested-by: Daniel Drake drake@endlessm.com Signed-off-by: Lv Zheng lv.zheng@intel.com [ rjw: Changelog & comments massage ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/acpi/ec.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c index 217b0bac33d9..d4e8a17d939a 100644 --- a/drivers/acpi/ec.c +++ b/drivers/acpi/ec.c @@ -1693,12 +1693,26 @@ static const struct acpi_device_id ec_device_ids[] = { {"", 0}, };
+/* + * This function is not Windows-compatible as Windows never enumerates the + * namespace EC before the main ACPI device enumeration process. It is + * retained for historical reason and will be deprecated in the future. + */ int __init acpi_ec_dsdt_probe(void) { acpi_status status; struct acpi_ec *ec; int ret;
+ /* + * If a platform has ECDT, there is no need to proceed as the + * following probe is not a part of the ACPI device enumeration, + * executing _STA is not safe, and thus this probe may risk of + * picking up an invalid EC device. + */ + if (boot_ec) + return -ENODEV; + ec = acpi_ec_alloc(); if (!ec) return -ENOMEM;