Re: [PATCH V4 1/7] acpi, pci: Setup MSI domain on a per-devices basis.

[Marc Zyngier]

On 04/04/16 09:52, Tomasz Nowicki wrote:
> It is now possible to provide information about which MSI controller to
> use on a per-device basis for DT. This patch supply this with ACPI support.
> 
> In order to handle MSI domain on per-devices basis we need to add
> PCI device requester ID (RID) mapper, MSI domain provider and corresponding
> registration:
> pci_acpi_msi_domain_get_msi_rid - maps PCI ID and returns MSI RID
> pci_acpi_register_msi_rid_mapper - registers RID mapper
> 
> pci_acpi_msi_get_device_domain - finds PCI device MSI domain
> pci_acpi_register_dev_msi_fwnode_provider - registers MSI domain finder
> 
> Then, it is plugged into MSI infrastructure.
> 
> To: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> To: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> Signed-off-by: Tomasz Nowicki <tn@xxxxxxxxxxxx>
> ---
>  drivers/pci/msi.c      | 10 +++++--
>  drivers/pci/pci-acpi.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci.h    | 11 ++++++++
>  3 files changed, 95 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index a080f44..07b59a3 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1364,8 +1364,8 @@ u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
>  	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
>  
>  	of_node = irq_domain_get_of_node(domain);
> -	if (of_node)
> -		rid = of_msi_map_rid(&pdev->dev, of_node, rid);
> +	rid = of_node ? of_msi_map_rid(&pdev->dev, of_node, rid) :
> +			pci_acpi_msi_domain_get_msi_rid(pdev, rid);
>  
>  	return rid;
>  }
> @@ -1381,9 +1381,13 @@ u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
>   */
>  struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
>  {
> +	struct irq_domain *dom;
>  	u32 rid = 0;
>  
>  	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
> -	return of_msi_map_get_device_domain(&pdev->dev, rid);
> +	dom = of_msi_map_get_device_domain(&pdev->dev, rid);
> +	if (!dom)
> +		dom = pci_acpi_msi_get_device_domain(pdev, rid);
> +	return dom;
>  }
>  #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 9a033e8..26f4552 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -731,6 +731,83 @@ struct irq_domain *pci_host_bridge_acpi_msi_domain(struct pci_bus *bus)
>  	return irq_find_matching_fwnode(fwnode, DOMAIN_BUS_PCI_MSI);
>  }
>  
> +static u32 (*pci_msi_map_dev_rid_cb)(struct pci_dev *pdev, u32 req_id);
> +
> +/**
> + * pci_acpi_register_msi_rid_mapper - Register callback to map the MSI
> + * requester id (RID)
> + * @fn:       Callback mapping a PCI device RID.
> + *
> + * This should be called by irqchip driver, which can provide firmware-defined
> + * topologies about MSI requester id (RID) on a per-device basis.
> + */
> +void pci_acpi_register_msi_rid_mapper(u32 (*fn)(struct pci_dev *, u32))
> +{
> +	pci_msi_map_dev_rid_cb = fn;
> +}
> +
> +/**
> + * pci_acpi_msi_domain_get_msi_rid - Get the MSI requester id (RID) of
> + * a PCI device
> + * @pdev:     The PCI device.
> + * @rid_in:   The PCI device request ID.
> + *
> + * This function uses the callback function registered by
> + * pci_acpi_register_msi_rid_mapper() to get the device RID based on ACPI
> + * supplied mapping.
> + * This should return rid_in on error or when there is no valid map.
> + */
> +u32 pci_acpi_msi_domain_get_msi_rid(struct pci_dev *pdev, u32 rid_in)
> +{
> +	if (!pci_msi_map_dev_rid_cb)
> +		return rid_in;
> +
> +	return pci_msi_map_dev_rid_cb(pdev, rid_in);
> +}
> +
> +static struct fwnode_handle *(*pci_msi_get_dev_fwnode_cb)(struct pci_dev *pdev,
> +							  u32 req_id);
> +
> +/**
> + * pci_acpi_register_dev_msi_fwnode_provider - Register callback to retrieve
> + * domain fwnode on the per-device basis
> + * @fn:       Callback matching a device to a fwnode that identifies a PCI
> + *            MSI domain.
> + *
> + * This should be called by irqchip driver, which can provide firmware-defined
> + * topologies about which MSI controller to use on a per-device basis.
> + */
> +void
> +pci_acpi_register_dev_msi_fwnode_provider(
> +			struct fwnode_handle *(*fn)(struct pci_dev *, u32))
> +{
> +	pci_msi_get_dev_fwnode_cb = fn;
> +}

I'm quite sceptical about this indirection. Either IORT is the only
mapping infrastructure that we can use for ACPI and we can then directly
call into it, or we can have several of them (which ones?) and we need
more than just this single slot.

So in any case, I don't think this is the right solution. As my
understanding is that IORT is the only source of RID remapping, we
should be able to directly call into the IORT code without this complexity.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...