On Thu, Sep 26, 2024 at 12:47:13PM -0400, Frank Li wrote:
> Introduce field 'cpu_untranslate_addr' in of_pci_range to retrieve
> untranslated CPU address information. This is required for hardware like
> i.MX8QXP to configure the PCIe controller ATU and eliminate the need for
> workaround address fixups in drivers. Currently, many drivers use
> hardcoded CPU addresses for fixups, but this information is already
> described in the Device Tree. With correct hardware descriptions, such
> fixups can be removed.
Instead of saying "required for hardware like i.MX8QXP", can we say
something specific about what this kind of hardware *does* that
requires this?
I *think* the point is that there's some address translation being
done between the primary and secondary sides of some bridge.
I think "many drivers use hardcoded CPU addresses for fixups"
basically means the .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.
> ┌─────────┐ ┌────────────┐
> ┌─────┐ │ │ IA: 0x8ff0_0000 │ │
> │ CPU ├───►│ BUS ├─────────────────┐ │ PCI │
> └─────┘ │ │ IA: 0x8ff8_0000 │ │ │
> CPU Addr │ Fabric ├─────────────┐ │ │ Controller │
> 0x7000_0000 │ │ │ │ │ │
> │ │ │ │ │ │ PCI Addr
> │ │ │ └──► CfgSpace ─┼────────────►
> │ ├─────────┐ │ │ │ 0
> │ │ │ │ │ │
> └─────────┘ │ └──────► IOSpace ─┼────────────►
> │ │ │ 0
> │ │ │
> └──────────► MemSpace ─┼────────────►
> IA: 0x8000_0000 │ │ 0x8000_0000
> └────────────┘
What does "IA" stand for?
I don't quite understand the mapping done by the "BUS Fabric" block.
It looks like you're saying the CPU Addr 0x7000_0000 is translated to
all three of IA 0x8ff0_0000, IA 0x8ff8_0000, and IA 0x8000_0000, but
that doesn't seem right.
> bus@5f000000 {
> compatible = "simple-bus";
> #address-cells = <1>;
> #size-cells = <1>;
> ranges = <0x5f000000 0x0 0x5f000000 0x21000000>,
> <0x80000000 0x0 0x70000000 0x10000000>;
>
> pcieb: 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>;
> ...
> };
> };
>
> 'cpu_untranslate_addr' in of_pci_range can indicate above diagram IA
> address information.
>
> Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> ---
> Change from v1 to v2
> - add cpu_untranslate_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..f4cb82f5313cf 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->cpu_untranslate_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..0683ce0c07f68 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 cpu_untranslate_addr;
> u64 size;
> u32 flags;
> };
>
> --
> 2.34.1
>
