[PATCH v19 01/10] PCI: endpoint: Set ID and of_node for function driver

[Manivannan Sadhasivam]

On Wed, Jul 02, 2025 at 10:40:53AM GMT, Frank Li wrote:
> On Wed, Jul 02, 2025 at 04:30:48PM +0530, Manivannan Sadhasivam wrote:
> > On Mon, Jun 09, 2025 at 12:34:13PM GMT, Frank Li wrote:
> > > Set device ID as 'vfunc_no << 3 | func_no' and use
> > > 'device_set_of_node_from_dev()' to set 'of_node' the same as the EPC parent
> > > device.
> > >
> > > Currently, EPF 'of_node' is NULL, but many functions depend on 'of_node'
> > > settings, such as DMA, IOMMU, and MSI. At present, all DMA allocation
> > > functions use the EPC's device node, but they should use the EPF one.
> > > For multiple function drivers, IOMMU/MSI should be different for each
> > > function driver.
> > >
> >
> > We don't define OF node for any function, so device_set_of_node_from_dev() also
> > ends up reusing the EPC node. So how can you make use of it in multi EPF setup?
> 
> In mfd devices, children devices reuse parent's of_node
> drivers/gpio/gpio-adp5585.c
> drivers/input/keyboard/adp5589-keys.c
> drivers/pwm/pwm-adp5585.c
> 
> multi EPF should be similar to create multi children devices of mfd.
> 

No, they are not similar. MFD are real physical devices, but EPFs are (so far)
software based entities.

> > I don't understand.
> 
> >
> > > If multiple function devices share the same EPC device, there will be
> > > no isolation between them. Setting the ID and 'of_node' prepares for
> > > proper support.
> 
> Only share the same of_node.
> 
> Actually pci host bridge have similar situation, all pci ep devices reuse
> bridge's of node. framework use rid to distringuish it. EPF can use device::id
> to do similar things.
> 
> Actually iommu face the similar problem. So far, there are not EP device enable
> iommu yet, because it needs special mapping.
> 
> Prevously, I consider create dymatic of_node for each EPF and copy iommu/msi
> information to each children. But when I see adp5585 case, I think direct
> use parent's of_node should be simple and good enough.
> 
> In future, I suggest add children dt binding for it. For example: EPF provide
> a mailbox interface. how other dts node to refer to this mailbox's phandle?
> 

As I said above, EPFs are not real devices. There is currently only one
exception, MHI, which is backed by a hardware entity. So we cannot add
devicetree nodes for EPF, unless each EPF is a hardware entity.

- Mani

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