linux-kernel - Re: [PATCH v9 3/7] PCI: Add parent_bus_offset to resource

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Message-ID: <Z6TtMyik/gv1VqGg@lizhi-Precision-Tower-5810>
Date: Thu, 6 Feb 2025 12:11:15 -0500
From: Frank Li <Frank.li@....com>
To: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, Niklas Cassel <cassel@...nel.org>
Subject: Re: [PATCH v9 3/7] PCI: Add parent_bus_offset to resource_entry

On Tue, Jan 28, 2025 at 05:07:36PM -0500, Frank Li wrote:
> Introduce `parent_bus_offset` in `resource_entry` and a new API,
> `pci_add_resource_parent_bus_offset()`, to provide necessary information
> for PCI controllers with address translation units.
>
> Typical PCI data flow involves:
>   CPU (CPU address) -> Bus Fabric (Intermediate address) ->
>   PCI Controller (PCI bus address) -> PCI Bus.
>
> While most bus fabrics preserve address consistency, some modify addresses
> to intermediate values. The `parent_bus_offset` enables PCI controllers to
> translate these intermediate addresses correctly to PCI bus addresses.
>
> Pave the road to remove hardcoded cpu_addr_fixup() and similar patterns in
> PCI controller drivers.
>
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---


Bjorn:

	How do you think this method to handle parent_bus_offset? so other
pci host rc driver should be easy to use it.

Frank

> change from v9 to v10
> - new patch
> ---
>  drivers/pci/bus.c            | 11 +++++++++--
>  drivers/pci/of.c             | 12 +++++++++++-
>  include/linux/pci.h          |  2 ++
>  include/linux/resource_ext.h |  1 +
>  4 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index 98910bc0fcc4e..52e88c391e256 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -31,8 +31,8 @@ struct pci_bus_resource {
>  	struct resource		*res;
>  };
>
> -void pci_add_resource_offset(struct list_head *resources, struct resource *res,
> -			     resource_size_t offset)
> +void pci_add_resource_parent_bus_offset(struct list_head *resources, struct resource *res,
> +					resource_size_t offset, resource_size_t parent_bus_offset)
>  {
>  	struct resource_entry *entry;
>
> @@ -43,8 +43,15 @@ void pci_add_resource_offset(struct list_head *resources, struct resource *res,
>  	}
>
>  	entry->offset = offset;
> +	entry->parent_bus_offset = parent_bus_offset;
>  	resource_list_add_tail(entry, resources);
>  }
> +
> +void pci_add_resource_offset(struct list_head *resources, struct resource *res,
> +			     resource_size_t offset)
> +{
> +	pci_add_resource_parent_bus_offset(resources, res, offset, 0);
> +}
>  EXPORT_SYMBOL(pci_add_resource_offset);
>
>  void pci_add_resource(struct list_head *resources, struct resource *res)
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index 7a806f5c0d201..aa4a2e266c55e 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -402,7 +402,17 @@ static int devm_of_pci_get_host_bridge_resources(struct device *dev,
>  			res->flags &= ~IORESOURCE_MEM_64;
>  		}
>
> -		pci_add_resource_offset(resources, res,	res->start - range.pci_addr);
> +		/*
> +		 * IORESOURCE_IO res->start is io space start address.
> +		 * IORESOURCE_MEM res->start is cpu start address, which is the
> +		 * same as range.cpu_addr.
> +		 *
> +		 * Use (range.cpu_addr - range.parent_bus_addr) to align both
> +		 * IO and MEM's parent_bus_offset always offset to cpu address.
> +		 */
> +
> +		pci_add_resource_parent_bus_offset(resources, res, res->start - range.pci_addr,
> +						   range.cpu_addr - range.parent_bus_addr);
>  	}
>
>  	/* Check for dma-ranges property */
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 47b31ad724fa5..0d7e67b47be47 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1510,6 +1510,8 @@ static inline void pci_release_config_region(struct pci_dev *pdev,
>  void pci_add_resource(struct list_head *resources, struct resource *res);
>  void pci_add_resource_offset(struct list_head *resources, struct resource *res,
>  			     resource_size_t offset);
> +void pci_add_resource_parent_bus_offset(struct list_head *resources, struct resource *res,
> +					resource_size_t offset, resource_size_t parent_bus_offset);
>  void pci_free_resource_list(struct list_head *resources);
>  void pci_bus_add_resource(struct pci_bus *bus, struct resource *res);
>  struct resource *pci_bus_resource_n(const struct pci_bus *bus, int n);
> diff --git a/include/linux/resource_ext.h b/include/linux/resource_ext.h
> index ff0339df56afc..b6ec6cc318203 100644
> --- a/include/linux/resource_ext.h
> +++ b/include/linux/resource_ext.h
> @@ -24,6 +24,7 @@ struct resource_entry {
>  	struct list_head	node;
>  	struct resource		*res;	/* In master (CPU) address space */
>  	resource_size_t		offset;	/* Translation offset for bridge */
> +	resource_size_t		parent_bus_offset; /* Parent bus address offset for bridge */
>  	struct resource		__res;	/* Default storage for res */
>  };
>
>
> --
> 2.34.1
>