On Fri, 2024-06-14 at 13:08 +0200, Rafael J. Wysocki wrote:
> On Thu, Jun 13, 2024 at 11:10 PM Suraj Jitindar Singh
> <surajjs@xxxxxxxxxx> wrote:
> >
> > Make is possible to use ACPI without having CONFIG_PCI set.
> >
> > When initialising ACPI the following call chain occurs:
> >
> > acpi_init() ->
> > acpi_bus_init() ->
> > acpi_load_tables() ->
> > acpi_ev_install_region_handlers() ->
> >
> > acpi_ev_install_region_handlers() calls
> > acpi_ev_install_space_handler() on
> > each of the default address spaces defined as:
> >
> > u8 acpi_gbl_default_address_spaces[ACPI_NUM_DEFAULT_SPACES] = {
> > ACPI_ADR_SPACE_SYSTEM_MEMORY,
> > ACPI_ADR_SPACE_SYSTEM_IO,
> > ACPI_ADR_SPACE_PCI_CONFIG,
> > ACPI_ADR_SPACE_DATA_TABLE
> > };
> >
> > However in acpi_ev_install_space_handler() the case statement for
> > ACPI_ADR_SPACE_PCI_CONFIG is ifdef'd as:
> >
> > #ifdef ACPI_PCI_CONFIGURED
> > case ACPI_ADR_SPACE_PCI_CONFIG:
> >
> > handler =
> > acpi_ex_pci_config_space_handler;
> > setup = acpi_ev_pci_config_region_setup;
> > break;
> > #endif
> >
> > ACPI_PCI_CONFIGURED is not defined if CONFIG_PCI is not enabled,
> > thus the
> > attempt to install the handler fails.
> >
> > Fix this by ifdef'ing ACPI_ADR_SPACE_PCI_CONFIG in the list of
> > default
> > address spaces.
>
> What if there are PCI operation regions in the AML on the platform?
> How are they going to be handled?
Hi,
Appreciate the response.
I think the short answer is that if there are PCI operation regions in
the AML on the platform then the kernel will need to be built with PCI
support (CONFIG_PCI) and if it isn't then there won't be a handler
installed and the operation will error.
Correct me if I'm wrong but it seems the intention of the patch series:
36ad7d2b9e9b ACPI: Move PCI reset to a separate function
86689776878f ACPI: Allow CONFIG_PCI to be unset for reboot
bd23fac3eaaa ACPICA: Remove PCI bits from ACPICA when CONFIG_PCI is
unset
5d32a66541c4 PCI/ACPI: Allow ACPI to be built without CONFIG_PCI set
was to decouple the dependency between CONFIG_PCI and CONFIG_ACPI.
bd23fac3eaaa ("ACPICA: Remove PCI bits from ACPICA when CONFIG_PCI is
unset") added an ifdef around the code to install the handler for the
PCI CONFIG region making it dependent on ACPI_PCI_CONFIGURED (and thus
CONFIG_PCI). Thus it is not possible to install the default handler for
the PCI CONFIG region unless CONFIG_PCI is set meaning it makes no
sense to have it in the list of default address spaces.
I can gather that this leads to 2 possibilities:
1. If there are PCI operation regions in the AML on the platform then
these will error on a kernel not compiled with CONFIG_PCI.
or,
2. The code to install the handler for the PCI CONFIG region should not
be ifdef'ed and should be executed irrespective of if the kernel is
compiled with CONFIG_PCI to allow for PCI CONFIG regions in the AML.
Thanks
>
> > Fixes: bd23fac3eaaa ("ACPICA: Remove PCI bits from ACPICA when
> > CONFIG_PCI is unset")
> > CC: stable@xxxxxxxxxxxxxxx # 5.0.x-
> > Signed-off-by: Suraj Jitindar Singh <surajjs@xxxxxxxxxx>
> > ---
> > drivers/acpi/acpica/evhandler.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/acpi/acpica/evhandler.c
> > b/drivers/acpi/acpica/evhandler.c
> > index 1c8cb6d924df..371093acb362 100644
> > --- a/drivers/acpi/acpica/evhandler.c
> > +++ b/drivers/acpi/acpica/evhandler.c
> > @@ -26,7 +26,9 @@ acpi_ev_install_handler(acpi_handle obj_handle,
> > u8 acpi_gbl_default_address_spaces[ACPI_NUM_DEFAULT_SPACES] = {
> > ACPI_ADR_SPACE_SYSTEM_MEMORY,
> > ACPI_ADR_SPACE_SYSTEM_IO,
> > +#ifdef ACPI_PCI_CONFIGURED
> > ACPI_ADR_SPACE_PCI_CONFIG,
> > +#endif
> > ACPI_ADR_SPACE_DATA_TABLE
> > };
> >
> > --
> > 2.34.1
> >
> >
