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

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Message-ID: <ne5yrjtdevmndqds4uwo2ppq6gay2wuwjouyf33lqr5g3nfkwr@lkwqlwqjqbmx>
Date: Wed, 2 Jul 2025 16:30:48 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Frank Li <Frank.Li@....com>
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 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?
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.
> 

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

- 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
> 
> 

-- 
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