Re: [PATCH v2 4/7] PCI/MSI: Make the pci_msi_map_rid_ctlr_node() interface firmware agnostic

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Thu, 18 Dec 2025 11:14:30 +0100
Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:

> To support booting with OF and ACPI seamlessly, GIC ITS parent code
> requires the PCI/MSI irqdomain layer to implement a function to retrieve
> an MSI controller fwnode and map an RID in a firmware agnostic way
> (ie pci_msi_map_rid_ctlr_node()).
> 
> Convert pci_msi_map_rid_ctlr_node() to an OF agnostic interface
> (fwnode_handle based) and update the GIC ITS MSI parent code to reflect
> the pci_msi_map_rid_ctlr_node() change.
> 
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Marc Zyngier <maz@kernel.org>
Hi Lorenzo,

A few minor comments inline.  All in the 'up to you' category.

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---

> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index a329060287b5..3136341e802c 100644
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -376,23 +376,35 @@ u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
>  }
>  
>  /**
> - * pci_msi_map_rid_ctlr_node - Get the MSI controller node and MSI requester id (RID)
> + * pci_msi_map_rid_ctlr_node - Get the MSI controller fwnode_handle and MSI requester id (RID)
> + * @domain:	The interrupt domain
>   * @pdev:	The PCI device
> - * @node:	Pointer to store the MSI controller device node
> + * @node:	Pointer to store the MSI controller fwnode_handle
>   *
> - * Use the firmware data to find the MSI controller node for @pdev.
> + * Use the firmware data to find the MSI controller fwnode_handle for @pdev.
>   * If found map the RID and initialize @node with it. @node value must
>   * be set to NULL on entry.
>   *
>   * Returns: The RID.
>   */
> -u32 pci_msi_map_rid_ctlr_node(struct pci_dev *pdev, struct device_node **node)
> +u32 pci_msi_map_rid_ctlr_node(struct irq_domain *domain, struct pci_dev *pdev,
> +			      struct fwnode_handle **node)
>  {
> +	struct device_node *of_node;
>  	u32 rid = pci_dev_id(pdev);
>  
>  	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
>  
> -	return of_msi_xlate(&pdev->dev, node, rid);
> +	of_node = irq_domain_get_of_node(domain);
> +	if (of_node) {

I haven't read on but my assumption is of_node is never used for anything else.
I'd make that explicit by not having the local variable.
	if (irq_domain_get_of_node(domain))

Might even be worth a comment to say this is just checking of is in use for the
domain in general?

> +		struct device_node *msi_ctlr_node = NULL;
> +
> +		rid = of_msi_xlate(&pdev->dev, &msi_ctlr_node, rid);
> +		if (msi_ctlr_node)

Do you need the protection? Ultimately that depends on whether
setting *node = NULL on failure to match is a problem.
It's a bit subtle, but if your new code matches behavior of old code
then *node was always NULL at entry to this function so setting it
to NULL again (which is what happens if ms_ctrl_node == NULL) should
be fine.

Maybe it's all a bit subtle though so perhaps the check is worth having.

> +			*node = of_fwnode_handle(msi_ctlr_node);
> +	}
> +
> +	return rid;
>  }
>  
>  /**
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 8003e3218c46..8ddb05d5c96a 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -702,7 +702,8 @@ void __pci_write_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
>  void pci_msi_mask_irq(struct irq_data *data);
>  void pci_msi_unmask_irq(struct irq_data *data);
>  u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
> -u32 pci_msi_map_rid_ctlr_node(struct pci_dev *pdev, struct device_node **node);
> +u32 pci_msi_map_rid_ctlr_node(struct irq_domain *domain, struct pci_dev *pdev,
> +			      struct fwnode_handle **node);
>  struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
>  void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
>  			   struct msi_desc *desc);
>