Re: [PATCH v2 5/5] PCI: Set native_pcie_hotplug up front based on pcie_ports_native

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Jul 14, 2025 at 04:50:45PM -0700, Sathyanarayanan Kuppuswamy wrote:
> 
> On 7/14/25 4:00 PM, Sathyanarayanan Kuppuswamy wrote:
> > 
> > On 7/13/25 7:31 AM, Lukas Wunner wrote:
> > > Bjorn suggests to "set host->native_pcie_hotplug up front based on
> > > CONFIG_HOTPLUG_PCI_PCIE and pcie_ports_native, and pciehp_is_native()
> > > would collapse to just an accessor for host->native_pcie_hotplug".
> > > 
> > > Unfortunately only half of this is possible:
> > > 
> > > The check for pcie_ports_native can indeed be moved out of
> > > pciehp_is_native() and into acpi_pci_root_create().
> > > 
> > > The check for CONFIG_HOTPLUG_PCI_PCIE however cannot be eliminated:
> > > 
> > > get_port_device_capability() needs to know whether platform firmware has
> > > granted PCIe Native Hot-Plug control to the operating system. If it has
> > > and CONFIG_HOTPLUG_PCI_PCIE is disabled, the function disables hotplug
> > > interrupts in case BIOS left them enabled.
> > > 
> > > If host->native_pcie_hotplug would be set up front based on
> > > CONFIG_HOTPLUG_PCI_PCIE, it would later on be impossible for
> > > get_port_device_capability() to tell whether it can safely disable hotplug
> > > interrupts:  It wouldn't know whether Native Hot-Plug control was granted.
> > 
> > Since pcie_ports_native is a PCI driver specific override option, I am not
> > sure it is worth referring to this option in ACPI driver, just to reduce the
> > number of pcie_ports_native checks from 2 to 1.
> 
> Never mind. It looks like the goal is to simplify the
> pciehp_is_native() call.

I would actually like to see more uses of pcie_ports_native removed.
It's basically an override of the OS/platform negotiation for control
of features, so I think it would make sense to test it somewhere in
the negotiate_os_control() rats nest or in acpi_pci_root_create().

> > > Link: https://lore.kernel.org/r/20250627025607.GA1650254@bhelgaas/
> > > Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> > > Signed-off-by: Lukas Wunner <lukas@wunner.de>
> > > ---
> > >   drivers/acpi/pci_root.c    | 3 ++-
> > >   drivers/pci/pci-acpi.c     | 3 ---
> > >   drivers/pci/pcie/portdrv.c | 2 +-
> > >   3 files changed, 3 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> > > index 74ade4160314..f3de0dc9c533 100644
> > > --- a/drivers/acpi/pci_root.c
> > > +++ b/drivers/acpi/pci_root.c
> > > @@ -1028,7 +1028,8 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
> > >           goto out_release_info;
> > >         host_bridge = to_pci_host_bridge(bus->bridge);
> > > -    if (!(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
> > > +    if (!pcie_ports_native &&
> > > +        !(root->osc_control_set & OSC_PCI_EXPRESS_NATIVE_HP_CONTROL))
> > >           host_bridge->native_pcie_hotplug = 0;
> > >       if (!(root->osc_control_set & OSC_PCI_SHPC_NATIVE_HP_CONTROL))
> > >           host_bridge->native_shpc_hotplug = 0;
> > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> > > index ed7ed66a595b..b513826ea293 100644
> > > --- a/drivers/pci/pci-acpi.c
> > > +++ b/drivers/pci/pci-acpi.c
> > > @@ -820,9 +820,6 @@ bool pciehp_is_native(struct pci_dev *bridge)
> > >       if (!IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
> > >           return false;
> > >   -    if (pcie_ports_native)
> > > -        return true;
> > > -
> > >       host = pci_find_host_bridge(bridge->bus);
> > >       return host->native_pcie_hotplug;
> > >   }
> > > diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
> > > index d1b68c18444f..fa83ebdcfecb 100644
> > > --- a/drivers/pci/pcie/portdrv.c
> > > +++ b/drivers/pci/pcie/portdrv.c
> > > @@ -223,7 +223,7 @@ static int get_port_device_capability(struct pci_dev *dev)
> > >       if (dev->is_pciehp &&
> > >           (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> > >            pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM) &&
> > > -        (pcie_ports_native || host->native_pcie_hotplug)) {
> > > +        host->native_pcie_hotplug) {
> > >           services |= PCIE_PORT_SERVICE_HP;
> > >             /*
> > 
> -- 
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer
>