[PATCH v2] ACPI: pci_root: Clear the acpi dependencies after PCI root bridge initialization on RISC-V

[Bjorn Helgaas]

On Tue, Jan 27, 2026 at 04:00:49PM +0100, Rafael J. Wysocki wrote:
> On Mon, Jan 12, 2026 at 3:17 PM huyuye <huyuye812 at 163.com> wrote:
> >
> > Hi Rafael,
> > Thank you for your thorough review and valuable comments on v1.
> > I've updated the patch as follows:
> > 1. Removed the redundant #ifdef CONFIG_ACPI and if (!acpi_disabled)
> > guard as you pointed out. The entire code block indeed already depends
> > on CONFIG_ACPI at a higher level, making the inner guard unnecessary.
> > 2. Moved acpi_dev_clear_dependencies to RISC-V specific architecture
> > code (driver/acpi/riscv/acpi_pci.c). This ensures that ACPI dependency
> > clearing is handled within the appropriate architectural context.
> >
> > Best regards
> > Signed-off-by: huyuye <huyuye812 at 163.com>
> > ---
> >  drivers/acpi/pci_root.c       |  6 ++++++
> >  drivers/acpi/riscv/Makefile   |  2 +-
> >  drivers/acpi/riscv/acpi_pci.c | 11 +++++++++++
> >  include/acpi/acpi_bus.h       |  1 +
> >  4 files changed, 19 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/acpi/riscv/acpi_pci.c
> >
> > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > index 9d7f85dadc48..a16eb9097cdc 100644
> > --- a/drivers/acpi/pci_root.c
> > +++ b/drivers/acpi/pci_root.c
> > @@ -30,6 +30,11 @@ static int acpi_pci_root_add(struct acpi_device *device,
> >                              const struct acpi_device_id *not_used);
> >  static void acpi_pci_root_remove(struct acpi_device *device);
> >
> > +
> > +void __weak arch_acpi_pci_root_add_clear_dep(struct acpi_device *device)
> > +{
> > +}
> > +
> >  static int acpi_pci_root_scan_dependent(struct acpi_device *adev)
> >  {
> >         acpiphp_check_host_bridge(adev);
> > @@ -760,6 +765,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
> >         pci_lock_rescan_remove();
> >         pci_bus_add_devices(root->bus);
> >         pci_unlock_rescan_remove();
> > +       arch_acpi_pci_root_add_clear_dep(device);
> 
> Actually, this could be as simple as
> 
>        if (IS_ENABLED(CONFIG_RISCV))
>               acpi_dev_clear_dependencies(device);
> 
> with a brief comment explaining why it is needed.
> 
> Bjorn, any thoughts?

The justification ("If a host bridge B depends on host bridge A (via
_DEP), this call allows bridge B to proceed with enumeration after
bridge A is fully initialized") doesn't sound specific to RISC-V.

For that matter, it doesn't sound specific to host bridges either.

The _DEP spec language is a bit vague.  ACPI r6.6, sec 6.5.8, says:

  _DEP evaluates to a package and designates device objects that OSPM
  should assign a higher priority in start ordering due to
  dependencies between devices (for example, related to future
  operation region accesses).

I don't know what "device start" means.  It sounds like this alludes
to the order in which OSPM runs some device start method?  _INI?
Should acpi_dev_clear_dependencies() be done at the point where that
device start method is run?

> >         return 1;
> >
> >  remove_dmar:
> > diff --git a/drivers/acpi/riscv/Makefile b/drivers/acpi/riscv/Makefile
> > index 1284a076fa88..5b1bd0298fb9 100644
> > --- a/drivers/acpi/riscv/Makefile
> > +++ b/drivers/acpi/riscv/Makefile
> > @@ -1,5 +1,5 @@
> >  # SPDX-License-Identifier: GPL-2.0-only
> > -obj-y                                  += rhct.o init.o irq.o
> > +obj-y                                  += rhct.o init.o irq.o acpi_pci.o
> >  obj-$(CONFIG_ACPI_PROCESSOR_IDLE)      += cpuidle.o
> >  obj-$(CONFIG_ACPI_CPPC_LIB)            += cppc.o
> >  obj-$(CONFIG_ACPI_RIMT)                        += rimt.o
> > diff --git a/drivers/acpi/riscv/acpi_pci.c b/drivers/acpi/riscv/acpi_pci.c
> > new file mode 100644
> > index 000000000000..368ff113e5c6
> > --- /dev/null
> > +++ b/drivers/acpi/riscv/acpi_pci.c
> > @@ -0,0 +1,11 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2026, ZTE Corporation
> > + *  Author: Yu Ye Hu <hu.yuye at zte.com.cn>
> > + */
> > +#include <linux/acpi.h>
> > +
> > +void arch_acpi_pci_root_add_clear_dep(struct acpi_device *device)
> > +{
> > +       acpi_dev_clear_dependencies(device);
> > +}
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index aad1a95e6863..c00b523a6ebd 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -996,6 +996,7 @@ int acpi_wait_for_acpi_ipmi(void);
> >
> >  int acpi_scan_add_dep(acpi_handle handle, struct acpi_handle_list *dep_devices);
> >  u32 arch_acpi_add_auto_dep(acpi_handle handle);
> > +void arch_acpi_pci_root_add_clear_dep(struct acpi_device *device);
> >  #else  /* CONFIG_ACPI */
> >
> >  static inline int register_acpi_bus_type(void *bus) { return 0; }
> > --
> > 2.43.0
> >