Introduce field 'parent_bus_addr' in of_pci_range to retrieve untranslated
CPU address information.

Refer to the diagram below to understand that the bus fabric in some
systems (like i.MX8QXP) does not use a 1:1 address map between input and
output.

Currently, many drivers use .cpu_addr_fixup() callback hardcodes that
translation in the code, e.g., "cpu_addr & CDNS_PLAT_CPU_TO_BUS_ADDR",
"cpu_addr + BUS_IATU_OFFSET", etc, even though those translations *should*
be described via DT.

The .cpu_addr_fixup() can be eliminated if DT correct reflect hardware
behavior and driver use 'parent_bus_addr' in of_pci_range.

            ┌─────────┐                    ┌────────────┐
 ┌─────┐    │         │ IA: 0x8ff0_0000    │            │
 │ CPU ├───►│   ┌────►├─────────────────┐  │ PCI        │
 └─────┘    │   │     │ IA: 0x8ff8_0000 │  │            │
  CPU Addr  │   │  ┌─►├─────────────┐   │  │ Controller │
0x7ff0_0000─┼───┘  │  │             │   │  │            │
            │      │  │             │   │  │            │   PCI Addr
0x7ff8_0000─┼──────┘  │             │   └──► CfgSpace  ─┼────────────►
            │         │             │      │            │    0
0x7000_0000─┼────────►├─────────┐   │      │            │
            └─────────┘         │   └──────► IOSpace   ─┼────────────►
             BUS Fabric         │          │            │    0
                                │          │            │
                                └──────────► MemSpace  ─┼────────────►
                        IA: 0x8000_0000    │            │  0x8000_0000
                                           └────────────┘

bus@5f000000 {
        compatible = "simple-bus";
        #address-cells = <1>;
        #size-cells = <1>;
        ranges = <0x5f000000 0x0 0x5f000000 0x21000000>,
                 <0x80000000 0x0 0x70000000 0x10000000>;

        pcie@5f010000 {
                compatible = "fsl,imx8q-pcie";
                reg = <0x5f010000 0x10000>, <0x8ff00000 0x80000>;
                reg-names = "dbi", "config";
                #address-cells = <3>;
                #size-cells = <2>;
                device_type = "pci";
                bus-range = <0x00 0xff>;
                ranges = <0x81000000 0 0x00000000 0x8ff80000 0 0x00010000>,
                         <0x82000000 0 0x80000000 0x80000000 0 0x0ff00000>;
	...
	};
};

'parent_bus_addr' in of_pci_range can indicate above diagram internal
address (IA) address information.

Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Change from v2 to v3
- cpu_untranslate_addr -> parent_bus_addr
- Add Rob's review tag
  I changed commit message base on Bjorn, if you have concern about review
added tag, let me know.

Change from v1 to v2
- add parent_bus_addr in of_pci_range, instead adding new API.
---
 drivers/of/address.c       | 2 ++
 include/linux/of_address.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 286f0c161e332..1a0229ee4e0b2 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -811,6 +811,8 @@ struct of_pci_range *of_pci_range_parser_one(struct of_pci_range_parser *parser,
 	else
 		range->cpu_addr = of_translate_address(parser->node,
 				parser->range + na);
+
+	range->parent_bus_addr = of_read_number(parser->range + na, parser->pna);
 	range->size = of_read_number(parser->range + parser->pna + na, ns);
 
 	parser->range += np;
diff --git a/include/linux/of_address.h b/include/linux/of_address.h
index 26a19daf0d092..13dd79186d02c 100644
--- a/include/linux/of_address.h
+++ b/include/linux/of_address.h
@@ -26,6 +26,7 @@ struct of_pci_range {
 		u64 bus_addr;
 	};
 	u64 cpu_addr;
+	u64 parent_bus_addr;
 	u64 size;
 	u32 flags;
 };

-- 
2.34.1

On Mon, Sep 30, 2024 at 02:44:53PM -0400, Frank Li wrote:
> Introduce field 'parent_bus_addr' in of_pci_range to retrieve untranslated
> CPU address information.
> 
> Refer to the diagram below to understand that the bus fabric in some
> systems (like i.MX8QXP) does not use a 1:1 address map between input and
> output.
> 
> Currently, many drivers use .cpu_addr_fixup() callback hardcodes that

s/drivers/controller drivers/

> translation in the code, e.g., "cpu_addr & CDNS_PLAT_CPU_TO_BUS_ADDR",
> "cpu_addr + BUS_IATU_OFFSET", etc, even though those translations *should*
> be described via DT.
> 

It'd be useful to mention which driver has the mentioned fixup as an example.

- Mani

-- 
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