On Thu, Dec 14, 2023 at 05:32:41PM +0000, Jonathan Cameron wrote: > On Wed, 13 Dec 2023 12:49:16 +0000 > Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> wrote: > > > From: James Morse <james.morse@xxxxxxx> > > > > Today the ACPI enumeration code 'visits' all devices that are present. > > > > This is a problem for arm64, where CPUs are always present, but not > > always enabled. When a device-check occurs because the firmware-policy > > has changed and a CPU is now enabled, the following error occurs: > > | acpi ACPI0007:48: Enumeration failure > > > > This is ultimately because acpi_dev_ready_for_enumeration() returns > > true for a device that is not enabled. The ACPI Processor driver > > will not register such CPUs as they are not 'decoding their resources'. > > > > Change acpi_dev_ready_for_enumeration() to also check the enabled bit. > > ACPI allows a device to be functional instead of maintaining the > > present and enabled bit. Make this behaviour an explicit check with > > a reference to the spec, and then check the present and enabled bits. > > This is needed to avoid enumerating present && functional devices that > > are not enabled. > > > > Signed-off-by: James Morse <james.morse@xxxxxxx> > > Tested-by: Miguel Luis <miguel.luis@xxxxxxxxxx> > > Tested-by: Vishnu Pajjuri <vishnu@xxxxxxxxxxxxxxxxxxxxxx> > > Tested-by: Jianyong Wu <jianyong.wu@xxxxxxx> > > Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> > > --- > > If this change causes problems on deployed hardware, I suggest an > > arch opt-in: ACPI_IGNORE_STA_ENABLED, that causes > > acpi_dev_ready_for_enumeration() to only check the present bit. > > My gut feeling (having made ACPI 'fixes' in the past that ran into > horribly broken firmware and had to be reverted) is reduce the blast > radius preemptively from the start. I'd love to live in a world were > that wasn't necessary but I don't trust all the generators of ACPI tables. > I'll leave it to Rafael and other ACPI experts suggest how narrow we should > make it though - arch opt in might be narrow enough. Yes, I think an arch opt-in would be the most sensible way forward, if Rafael concurs with that idea. I notice that what I wrote there was actually an opt-out. I'll fix that. > > + /* > > + * ACPI 6.5's 6.3.7 "_STA (Device Status)" allows firmware to return > > + * (!present && functional) for certain types of devices that should be > > + * enumerated. Note that the enabled bit can't be sert until the present > > set until Thanks for spotting that, fixed. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
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