Re: [PATCH v7 1/7] of: address: Add parent_bus_addr to struct of_pci_range

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Tue, Oct 29, 2024 at 12:36:34PM -0400, Frank Li wrote:
> Introduce field 'parent_bus_addr' in struct of_pci_range to retrieve parent
> bus 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 controller drivers use .cpu_addr_fixup() callback hardcodes
> that translation in the code, e.g., "cpu_addr & CDNS_PLAT_CPU_TO_BUS_ADDR"
> (drivers/pci/controller/cadence/pcie-cadence-plat.c),
> "cpu_addr + BUS_IATU_OFFSET"(drivers/pci/controller/dwc/pcie-intel-gw.c),
> 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 struct of_pci_range.
> 
>             ┌─────────┐                    ┌────────────┐
>  ┌─────┐    │         │ IA: 0x8ff8_0000    │            │
>  │ CPU ├───►│   ┌────►├─────────────────┐  │ PCI        │
>  └─────┘    │   │     │ IA: 0x8ff0_0000 │  │            │
>   CPU Addr  │   │  ┌─►├─────────────┐   │  │ Controller │
> 0x7ff8_0000─┼───┘  │  │             │   │  │            │
>             │      │  │             │   │  │            │   PCI Addr
> 0x7ff0_0000─┼──────┘  │             │   └──► IOSpace   ─┼────────────►
>             │         │             │      │            │    0
> 0x7000_0000─┼────────►├─────────┐   │      │            │
>             └─────────┘         │   └──────► CfgSpace  ─┼────────────►
>              BUS Fabric         │          │            │    0
>                                 │          │            │
>                                 └──────────► MemSpace  ─┼────────────►
>                         IA: 0x8000_0000    │            │  0x8000_0000
>                                            └────────────┘
> 
> bus@5f000000 {
>         compatible = "simple-bus";
>         #address-cells = <1>;
>         #size-cells = <1>;
>         ranges = <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 struct 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>

Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

- Mani

> ---
> Change from v5 to v7
> -none
> 
> Change from v4 to v5
> - remove confused  <0x5f000000 0x0 0x5f000000 0x21000000>
> - change address order to 7ff8_0000, 7ff0_0000, 7000_0000
> - In commit message use parent bus addres
> 
> Change from v3 to v4
> - improve commit message by driver source code path.
> 
> 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 struct 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
> 

-- 
மணிவண்ணன் சதாசிவம்