Re: [PATCH v12 06/13] PCI: dwc: Add dw_pcie_parent_bus_offset() checking and debug

Manivannan Sadhasivam
2025-03-24T17:32:35Z

On Sat, Mar 15, 2025 at 03:15:41PM -0500, Bjorn Helgaas wrote:
> From: Frank Li <Frank.Li@nxp.com>
>
> dw_pcie_parent_bus_offset() looks up the parent bus address of a PCI
> controller 'reg' property in devicetree. If implemented, .cpu_addr_fixup()
> is a hard-coded way to get the parent bus address corresponding to a CPU
> physical address.
>
> Add debug code to compare the address from .cpu_addr_fixup() with the
> address from devicetree. If they match, warn that .cpu_addr_fixup() is
> redundant and should be removed; if they differ, warn that something is
> wrong with the devicetree.
>
> If .cpu_addr_fixup() is not implemented, the parent bus address should be
> identical to the CPU physical address because we previously ignored the
> parent bus address from devicetree. If the devicetree has a different
> parent bus address, warn about it being broken.
>
> [bhelgaas: split debug to separate patch for easier future revert, commit
> log]
> Link: https://lore.kernel.org/r/20250313-pci_fixup_addr-v11-5-01d2313502ab@nxp.com
> Signed-off-by: Frank Li <Frank.Li@nxp.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
> drivers/pci/controller/dwc/pcie-designware.c | 26 +++++++++++++++++++-
> drivers/pci/controller/dwc/pcie-designware.h | 13 ++++++++++
> 2 files changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 0a35e36da703..985264c88b92 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -1114,7 +1114,8 @@ resource_size_t dw_pcie_parent_bus_offset(struct dw_pcie *pci,
> struct device *dev = pci->dev;
> struct device_node *np = dev->of_node;
> int index;
> - u64 reg_addr;
> + u64 reg_addr, fixup_addr;
> + u64 (*fixup)(struct dw_pcie *pcie, u64 cpu_addr);
>
> /* Look up reg_name address on parent bus */
> index = of_property_match_string(np, "reg-names", reg_name);
> @@ -1126,5 +1127,28 @@ resource_size_t dw_pcie_parent_bus_offset(struct dw_pcie *pci,
>
> of_property_read_reg(np, index, &reg_addr, NULL);
>
> + fixup = pci->ops->cpu_addr_fixup;
> + if (fixup) {
> + fixup_addr = fixup(pci, cpu_phy_addr);
> + if (reg_addr == fixup_addr) {
> + dev_warn(dev, "%#010llx %s reg[%d] == %#010llx; %ps is redundant\n",
> + cpu_phy_addr, reg_name, index,
> + fixup_addr, fixup);
> + } else {
> + dev_warn(dev, "%#010llx %s reg[%d] != %#010llx fixed up addr; devicetree is broken\n",
> + cpu_phy_addr, reg_name,
> + index, fixup_addr);
> + reg_addr = fixup_addr;
> + }
> + } else if (!pci->use_parent_dt_ranges) {

Is this check still valid? 'use_parent_dt_ranges' is only used here for
validation. Moreover, if the fixup is not available, we should be able to
safely return 'cpu_phy_addr - reg_addr' unconditionally.

> + if (reg_addr != cpu_phy_addr) {
> + dev_warn(dev, "devicetree has incorrect translation; please check parent \"ranges\" property. CPU physical addr %#010llx, parent bus addr %#010llx\n",
> + cpu_phy_addr, reg_addr);
> + return 0;
> + }
> + }
> +
> + dev_info(dev, "%s parent bus offset is %#010llx\n",
> + reg_name, cpu_phy_addr - reg_addr);

This info is useless on platforms having no translation between CPU and PCI
controller. The offset will always be 0.

- Mani

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