Re: [PATCH v8 3/7] PCI: dwc: ep: Add bus_addr_base for outbound window

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Nov 19, 2024 at 02:44:21PM -0500, Frank Li wrote:
>                    Endpoint
>   ┌───────────────────────────────────────────────┐
>   │                             pcie-ep@5f010000  │
>   │                             ┌────────────────┐│
>   │                             │   Endpoint     ││
>   │                             │   PCIe         ││
>   │                             │   Controller   ││
>   │           bus@5f000000      │                ││
>   │           ┌──────────┐      │                ││
>   │           │          │ Outbound Transfer     ││
>   │┌─────┐    │  Bus     ┼─────►│ ATU  ──────────┬┬─────►
>   ││     │    │  Fabric  │Bus   │                ││PCI Addr
>   ││ CPU ├───►│          │Addr  │                ││0xA000_0000
>   ││     │CPU │          │0x8000_0000            ││
>   │└─────┘Addr└──────────┘      │                ││
>   │       0x7000_0000           └────────────────┘│
>   └───────────────────────────────────────────────┘
> 
> Use 'ranges' property in DT to configure the iATU outbound window address.
> The bus fabric generally passes the same address to the PCIe EP controller,
> but some bus fabrics map the address before sending it to the PCIe EP
> controller.
> 
> Above diagram, CPU write data to outbound windows address 0x7000_0000, Bus
> fabric map it to 0x8000_0000. ATU should use bus address 0x8000_0000 as
> input address and map to PCI address 0xA000_0000.
> 
> Previously, 'cpu_addr_fixup()' was used to handle address conversion. Now,
> the device tree provides this information, preferring a common method.
> 
> bus@5f000000 {
> 	compatible = "simple-bus";
> 	ranges = <0x80000000 0x0 0x70000000 0x10000000>;
> 
> 	pcie-ep@5f010000 {
> 		reg = <0x80000000 0x10000000>;
> 		reg-names ="addr_space";
> 		...
> 	};
> 	...
> };
> 
> 'ranges' in bus@5f000000 descript how address map from CPU address to bus
> address.

Shouldn't there also be a pcie-ep@5f010000 'ranges' property to
describe the translation for the window from bus addr 0x8000_0000 to
PCI addr 0xA000_0000?

I assume the pcie-ep@5f010000 controller also has its own registers in
the bus addr space, separate from the window to PCI, and its 'reg'
property would describe those?

The similar patch at [1] includes:

  pcie@5f010000 {
    reg = <0x5f010000 0x10000>, <0x8ff00000 0x80000>;

I assumed that [bus 0x5f010000-0x5f01ffff] is PCIe controller register
space and [bus 0x8ff00000-0x8ff7ffff] is ECAM space.

But that can't be right because ECAM requires 1MB per bus, and
[bus 0x8ff00000-0x8ff7ffff] is only 512KB.

> Use `of_property_read_reg()` to obtain the bus address and set it to the
> ATU correctly, eliminating the need for vendor-specific cpu_addr_fixup().

Why is this different from [1], where parent_bus_addr comes from the
'ranges' property?  Isn't this the same exact kind of address
translation for both RC and EP mode?

> Add 'using_dtbus_info' to indicate device tree reflect correctly bus
> address translation in case break compatibility.

'using_dtbus_info' doesn't exist; I assume this should be
'use_parent_dt_ranges'?

Sorry I'm so confused, please help me out :)

[1] https://lore.kernel.org/r/20241119-pci_fixup_addr-v8-1-c4bfa5193288@nxp.com

> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> ---
> Change from v7 to v8
> - Add Mani's reviewedby tag
> - s/convert/map in commit message
> - update comments for of_property_read_reg()
> - use 'use_parent_dt_ranges'
> 
> Change from v6 to v7
> - none
> 
> Change from v5 to v6
> - update diagram
> - Add comments for of_property_read_reg()
> - Remove unrelated 0x5f00_0000 in commit message
> 
> Change from v3 to v4
> - change bus_addr_base to u64 to fix 32bit build error
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202410230328.BTHareG1-lkp@intel.com/
> 
> Change from v2 to v3
> - Add using_dtbus_info to control if use device tree bus ranges
> information.
> ---
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 18 +++++++++++++++++-
>  drivers/pci/controller/dwc/pcie-designware.h    |  1 +
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 43ba5c6738df1..42719ad263b11 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -9,6 +9,7 @@
>  #include <linux/align.h>
>  #include <linux/bitfield.h>
>  #include <linux/of.h>
> +#include <linux/of_address.h>
>  #include <linux/platform_device.h>
>  
>  #include "pcie-designware.h"
> @@ -294,7 +295,7 @@ static int dw_pcie_ep_map_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  
>  	atu.func_no = func_no;
>  	atu.type = PCIE_ATU_TYPE_MEM;
> -	atu.cpu_addr = addr;
> +	atu.cpu_addr = addr - ep->phys_base + ep->bus_addr_base;
>  	atu.pci_addr = pci_addr;
>  	atu.size = size;
>  	ret = dw_pcie_ep_outbound_atu(ep, &atu);
> @@ -861,6 +862,7 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  	struct device *dev = pci->dev;
>  	struct platform_device *pdev = to_platform_device(dev);
>  	struct device_node *np = dev->of_node;
> +	int index;
>  
>  	INIT_LIST_HEAD(&ep->func_list);
>  
> @@ -873,6 +875,20 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
>  		return -EINVAL;
>  
>  	ep->phys_base = res->start;
> +	ep->bus_addr_base = ep->phys_base;
> +
> +	if (pci->use_parent_dt_ranges) {
> +		index = of_property_match_string(np, "reg-names", "addr_space");
> +		if (index < 0)
> +			return -EINVAL;
> +
> +		/*
> +		 * Get the untranslated bus address from devicetree to use it
> +		 * as the iATU CPU address in dw_pcie_ep_map_addr().
> +		 */
> +		of_property_read_reg(np, index, &ep->bus_addr_base, NULL);
> +	}
> +
>  	ep->addr_size = resource_size(res);
>  
>  	if (ep->ops->pre_init)
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 4f31d4259a0de..5c14ed2cb91ed 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -410,6 +410,7 @@ struct dw_pcie_ep {
>  	struct list_head	func_list;
>  	const struct dw_pcie_ep_ops *ops;
>  	phys_addr_t		phys_base;
> +	u64			bus_addr_base;
>  	size_t			addr_size;
>  	size_t			page_size;
>  	u8			bar_to_atu[PCI_STD_NUM_BARS];
> 
> -- 
> 2.34.1
>