Subject: Re: [PATCH V4 1/7] acpi, pci: Setup MSI domain on a per-devices
 basis.
To: Marc Zyngier <marc.zyngier@arm.com>, tglx@linutronix.de,
        jason@lakedaemon.net, rjw@rjwysocki.net, lorenzo.pieralisi@arm.com,
        robert.richter@caviumnetworks.com, shijie.huang@arm.com,
        Suravee.Suthikulpanit@amd.com, hanjun.guo@linaro.org
References: <1459759975-24097-1-git-send-email-tn@semihalf.com>
 <1459759975-24097-2-git-send-email-tn@semihalf.com>
 <570E1CF3.3060102@arm.com>
Cc: al.stone@linaro.org, mw@semihalf.com, graeme.gregory@linaro.org,
        Catalin.Marinas@arm.com, will.deacon@arm.com,
        linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, ddaney.cavm@gmail.com,
        okaya@codeaurora.org
From: Tomasz Nowicki <tn@semihalf.com>
Message-ID: <570E241D.9000902@semihalf.com>
Date: Wed, 13 Apr 2016 12:49:01 +0200
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On 13.04.2016 12:18, Marc Zyngier wrote:
> 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@google.com>
>> To: Rafael J. Wysocki <rjw@rjwysocki.net>
>> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
>> ---
>>   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 Marc. I am not aware of any other RID remapper too. I will drop 
this layer and call IORT directly.

Tomasz