linux-kernel - Re: [PATCH v19 01/10] PCI: endpoint: Set ID and of

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Message-ID: <aGVE6veZm3bL0mVJ@lizhi-Precision-Tower-5810>
Date: Wed, 2 Jul 2025 10:40:53 -0400
From: Frank Li <Frank.li@....com>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: Kishon Vijay Abraham I <kishon@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Anup Patel <apatel@...tanamicro.com>, Marc Zyngier <maz@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
	Shuah Khan <shuah@...nel.org>, Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Rob Herring <robh@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Niklas Cassel <cassel@...nel.org>, dlemoal@...nel.org,
	jdmason@...zu.us, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
	linux-kselftest@...r.kernel.org, imx@...ts.linux.dev,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v19 01/10] PCI: endpoint: Set ID and of_node for function
 driver

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.

> 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?


> >
>
> I don't know who you can provide *isolation* by reusing the EPC OF node. It is
> same as using the EPC node directly.

why it is same?

Frank
>
> - Mani
>
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> > change from v14 to v16
> > - none
> >
> > change from v13 to v14
> > new patch
> > ---
> >  drivers/pci/endpoint/pci-epf-core.c | 4 ++++
> >  include/linux/pci-epf.h             | 2 ++
> >  2 files changed, 6 insertions(+)
> >
> > diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
> > index 577a9e490115c..95fb3d7c1d45e 100644
> > --- a/drivers/pci/endpoint/pci-epf-core.c
> > +++ b/drivers/pci/endpoint/pci-epf-core.c
> > @@ -120,12 +120,16 @@ int pci_epf_bind(struct pci_epf *epf)
> >  		epf_vf->sec_epc_func_no = epf->sec_epc_func_no;
> >  		epf_vf->epc = epf->epc;
> >  		epf_vf->sec_epc = epf->sec_epc;
> > +		epf_vf->dev.id = PCI_EPF_DEVID(epf->func_no, vfunc_no);
> > +		device_set_of_node_from_dev(&epf_vf->dev, epc->dev.parent);
> >  		ret = epf_vf->driver->ops->bind(epf_vf);
> >  		if (ret)
> >  			goto ret;
> >  		epf_vf->is_bound = true;
> >  	}
> >
> > +	epf->dev.id = PCI_EPF_DEVID(epf->func_no, 0);
> > +	device_set_of_node_from_dev(&epf->dev, epc->dev.parent);
> >  	ret = epf->driver->ops->bind(epf);
> >  	if (ret)
> >  		goto ret;
> > diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
> > index 749cee0bcf2cc..c0864935c6864 100644
> > --- a/include/linux/pci-epf.h
> > +++ b/include/linux/pci-epf.h
> > @@ -216,6 +216,8 @@ static inline void *epf_get_drvdata(struct pci_epf *epf)
> >  	return dev_get_drvdata(&epf->dev);
> >  }
> >
> > +#define PCI_EPF_DEVID(func_no, vfunc_no) ((vfunc_no) << 3 | (func_no))
> > +
> >  struct pci_epf *pci_epf_create(const char *name);
> >  void pci_epf_destroy(struct pci_epf *epf);
> >  int __pci_epf_register_driver(struct pci_epf_driver *driver,
> >
> > --
> > 2.34.1
> >
> >
>
> --
> மணிவண்ணன் சதாசிவம்