On Mon, May 05, 2025 at 12:03:13PM +0200, Rafael J. Wysocki wrote: > On Sat, May 3, 2025 at 9:10 PM Ricardo Neri > <ricardo.neri-calderon@xxxxxxxxxxxxxxx> wrote: > > > > The bootstrap processor uses acpi_wakeup_cpu() to indicate to firmware that > > it wants to boot a secondary CPU using a mailbox as described in the > > Multiprocessor Wakeup Structure of the ACPI specification. > > > > The wakeup mailbox does not strictly require support from ACPI. > > Well, except that it is defined by the ACPI specification. That is true. > > > The platform firmware can implement a mailbox compatible in structure and > > operation and enumerate it using other mechanisms such a DeviceTree graph. > > So is there a specification defining this mechanism? > > It is generally not sufficient to put the code and DT bindings > unilaterally into the OS and expect the firmware to follow suit. > This mechanism is described in the section 4.3.5 of the Intel TDX Virtual Firmware Design Guide [1], but it refeers to the ACPI specification for the interface. > > Move the code used to setup and use the mailbox out of the ACPI > > directory to use it when support for ACPI is not available or needed. > > I think that the code implementing interfaces defined by the ACPI > specification is not generic and so it should not be built when the > kernel is configured without ACPI support. Support for ACPI would not be used on systems describing hardware using a DeviceTree graph. My goal is to have a common interface that both DT and ACPI can use. I think what is missing is that common interface. Would it be preferred to have a separate implementation that is functionally equivalent? Thanks and BR, Ricardo [1]. https://cdrdv2-public.intel.com/733585/tdx-virtual-firmware-design-guide-rev-004-20231206.pdf
