Re: [PATCH] PCI: host-generic: Move bridge allocation outside of pci_host_common_init()

[Marc Zyngier <maz@kernel.org>]

On Thu, 20 Nov 2025 17:58:42 +0000,
Radu Rendec <rrendec@redhat.com> wrote:
> 
> On Thu, 2025-11-20 at 11:36 +0000, Marc Zyngier wrote:
> > Having the host bridge allocation inside pci_host_common_init() results
> > in a lot of complexity in the pcie-apple driver (the only direct user
> > of this function outside of code PCI code).
>                               ^^^^
> nit: s/code/core :)
> 
> > It forces the allocation of driver-specific tracking structures outside
> > of the bridge allocation, which in turns requires it to use inneficient
> > data structures to match the bridge and the private structre as needed.
> > 
> > Instead, let the bridge structure be passed to pci_host_common_init(),
> > allowing the driver to allocate it together with the private data,
> > as it is usually intended. The driver can then retrieve the bridge
> > via the owning device attached to the PCI config window structure.
> > This allows the pcie-apple driver to be significantly simplified.
> > 
> > Both core and driver code are changed in one go to avoid going via
> > a transitional interface.
> > 
> > Link: https://lore.kernel.org/r/86jyzms036.wl-maz@kernel.org
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Cc: Radu Rendec <rrendec@redhat.com>
> > Cc: Bjorn Helgaas <bhelgaas@google.com>
> > Cc: Manivannan Sadhasivam <mani@kernel.org>
> > Cc: Rob Herring <robh@kernel.org>
> > Cc: Krzysztof Wilczyński <kwilczynski@kernel.org>
> > Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
> > ---
> >  drivers/pci/controller/pci-host-common.c | 13 ++++----
> >  drivers/pci/controller/pci-host-common.h |  1 +
> >  drivers/pci/controller/pcie-apple.c      | 42 ++++--------------------
> >  3 files changed, 14 insertions(+), 42 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
> > index 810d1c8de24e9..c473e7c03baca 100644
> > --- a/drivers/pci/controller/pci-host-common.c
> > +++ b/drivers/pci/controller/pci-host-common.c
> > @@ -53,16 +53,12 @@ struct pci_config_window *pci_host_common_ecam_create(struct device *dev,
> >  EXPORT_SYMBOL_GPL(pci_host_common_ecam_create);
> >  
> >  int pci_host_common_init(struct platform_device *pdev,
> > +			 struct pci_host_bridge *bridge,
> >  			 const struct pci_ecam_ops *ops)
> >  {
> >  	struct device *dev = &pdev->dev;
> > -	struct pci_host_bridge *bridge;
> >  	struct pci_config_window *cfg;
> >  
> > -	bridge = devm_pci_alloc_host_bridge(dev, 0);
> > -	if (!bridge)
> > -		return -ENOMEM;
> > -
> >  	of_pci_check_probe_only();
> >  
> >  	platform_set_drvdata(pdev, bridge);
> > @@ -85,12 +81,17 @@ EXPORT_SYMBOL_GPL(pci_host_common_init);
> >  int pci_host_common_probe(struct platform_device *pdev)
> >  {
> >  	const struct pci_ecam_ops *ops;
> > +	struct pci_host_bridge *bridge;
> >  
> >  	ops = of_device_get_match_data(&pdev->dev);
> >  	if (!ops)
> >  		return -ENODEV;
> >  
> > -	return pci_host_common_init(pdev, ops);
> > +	bridge = devm_pci_alloc_host_bridge(&pdev->dev, 0);
> > +	if (!bridge)
> > +		return -ENOMEM;
> > +
> > +	return pci_host_common_init(pdev, bridge, ops);
> >  }
> >  EXPORT_SYMBOL_GPL(pci_host_common_probe);
> >  
> > diff --git a/drivers/pci/controller/pci-host-common.h b/drivers/pci/controller/pci-host-common.h
> > index 51c35ec0cf37d..b5075d4bd7eb3 100644
> > --- a/drivers/pci/controller/pci-host-common.h
> > +++ b/drivers/pci/controller/pci-host-common.h
> > @@ -14,6 +14,7 @@ struct pci_ecam_ops;
> >  
> >  int pci_host_common_probe(struct platform_device *pdev);
> >  int pci_host_common_init(struct platform_device *pdev,
> > +			 struct pci_host_bridge *bridge,
> >  			 const struct pci_ecam_ops *ops);
> >  void pci_host_common_remove(struct platform_device *pdev);
> >  
> > diff --git a/drivers/pci/controller/pcie-apple.c b/drivers/pci/controller/pcie-apple.c
> > index 0380d300adca6..a902aa81a497e 100644
> > --- a/drivers/pci/controller/pcie-apple.c
> > +++ b/drivers/pci/controller/pcie-apple.c
> > @@ -206,9 +206,6 @@ struct apple_pcie_port {
> >  	int			idx;
> >  };
> >  
> > -static LIST_HEAD(pcie_list);
> > -static DEFINE_MUTEX(pcie_list_lock);
> > -
> >  static void rmw_set(u32 set, void __iomem *addr)
> >  {
> >  	writel_relaxed(readl_relaxed(addr) | set, addr);
> > @@ -724,32 +721,9 @@ static int apple_msi_init(struct apple_pcie *pcie)
> >  	return 0;
> >  }
> >  
> > -static void apple_pcie_register(struct apple_pcie *pcie)
> > -{
> > -	guard(mutex)(&pcie_list_lock);
> > -
> > -	list_add_tail(&pcie->entry, &pcie_list);
> > -}
> > -
> > -static void apple_pcie_unregister(struct apple_pcie *pcie)
> > -{
> > -	guard(mutex)(&pcie_list_lock);
> > -
> > -	list_del(&pcie->entry);
> > -}
> > -
> >  static struct apple_pcie *apple_pcie_lookup(struct device *dev)
> >  {
> > -	struct apple_pcie *pcie;
> > -
> > -	guard(mutex)(&pcie_list_lock);
> > -
> > -	list_for_each_entry(pcie, &pcie_list, entry) {
> > -		if (pcie->dev == dev)
> > -			return pcie;
> > -	}
> > -
> > -	return NULL;
> > +	return pci_host_bridge_priv(dev_get_drvdata(dev));
> >  }
> > 
> > 
> 
> You forgot to remove the `entry` field from struct apple_pcie. It's no
> longer needed now that pcie_list is gone.

Ah, good point. Fixed.

> 
> >  
> >  static struct apple_pcie_port *apple_pcie_get_port(struct pci_dev *pdev)
> > @@ -875,13 +849,15 @@ static const struct pci_ecam_ops apple_pcie_cfg_ecam_ops = {
> >  static int apple_pcie_probe(struct platform_device *pdev)
> >  {
> >  	struct device *dev = &pdev->dev;
> > +	struct pci_host_bridge *bridge;
> >  	struct apple_pcie *pcie;
> >  	int ret;
> >  
> > -	pcie = devm_kzalloc(dev, sizeof(*pcie), GFP_KERNEL);
> > -	if (!pcie)
> > +	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*pcie));
> > +	if (!bridge)
> >  		return -ENOMEM;
> >  
> > +	pcie = pci_host_bridge_priv(bridge);
> >  	pcie->dev = dev;
> >  	pcie->hw = of_device_get_match_data(dev);
> >  	if (!pcie->hw)
> > @@ -897,13 +873,7 @@ static int apple_pcie_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		return ret;
> >  
> > -	apple_pcie_register(pcie);
> > -
> > -	ret = pci_host_common_init(pdev, &apple_pcie_cfg_ecam_ops);
> > -	if (ret)
> > -		apple_pcie_unregister(pcie);
> > -
> > -	return ret;
> > +	return pci_host_common_init(pdev, bridge, &apple_pcie_cfg_ecam_ops);
> >  }
> >  
> >  static const struct of_device_id apple_pcie_of_match[] = {
> 
> With those two nitpicks addressed,
> 
> Reviewed-by: Radu Rendec <rrendec@redhat.com>

Thanks. I'll repost this patch some time next week, as this is only an
optimisation, not really a fix.

> 
> And thanks again for spending time on this and creating the patch.

Nerd-sniping is a sport, it seems... ;-)

Cheers,

	M.


-- 
Without deviation from the norm, progress is not possible.