On Mon, Oct 03, 2022 at 04:42:14PM +0200, Hans de Goede wrote: > ACPI-2.0 says that the EC OpRegion handler must be available immediately > (like the standard default OpRegion handlers): > > Quoting from the ACPI spec version 6.3: "6.5.4 _REG (Region) ... (Side note: As of today the revision 6.5 of the ACPI specification is available) > 2. OSPM must make Embedded Controller operation regions, accessed via > the Embedded Controllers described in ECDT, available before executing > any control method. These operation regions may become inaccessible > after OSPM runs _REG(EmbeddedControl, 0)." > > So acpi_bus_init() calls acpi_ec_ecdt_probe(), which calls > acpi_install_address_space_handler() to install the EC's OpRegion > handler, early on. > > This not only installs the OpRegion handler, but also calls the EC's > _REG method. The _REG method call is a problem because it may rely on > initialization done by the _INI methods of one of the PCI / _SB root devs, > see for example: https://bugzilla.kernel.org/show_bug.cgi?id=214899 . > > Generally speaking _REG methods are executed when the ACPI-device they > are part of has a driver bound to it. Where as _INI methods must be > executed at table load time (according to the spec). The problem here > is that the early acpi_install_address_space_handler() call causes > the _REG handler to run too early. > > To allow fixing this the ACPICA code now allows to split the OpRegion > handler installation and the executing of _REG into 2 separate steps. > > This commit uses this ACPICA functionality to fix the EC probe ordering > by delaying the executing of _REG for ECDT described ECs till the matching > EC device in the DSDT gets parsed and acpi_ec_add() for it gets called. > This moves the calling of _REG for the EC on devices with an ECDT to > the same point in time where it is called on devices without an ECDT table. ... > + if (call_reg && !test_bit(EC_FLAGS_EC_REG_CALLED, &ec->flags)) { > + acpi_execute_reg_methods(ec->handle, ACPI_ADR_SPACE_EC); > + set_bit(EC_FLAGS_EC_REG_CALLED, &ec->flags); Just to be sure: do you need atomic operation here? Does it prevent of any kind of races? Because if it had been the case, it would have been done via test_and_set_bit() rather than testing and setting separated. > + } -- With Best Regards, Andy Shevchenko
