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

[Frank Li]

On Tue, Mar 18, 2025 at 10:38:20AM -0500, Bjorn Helgaas wrote:
> On Sat, Mar 15, 2025 at 03:15:41PM -0500, Bjorn Helgaas wrote:
> > From: Frank Li <Frank.Li@xxxxxxx>
> >
> > 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.
>
> > +++ 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",
>
> On second thought, I think this one should be a dev_info(), not a
> dev_warn().  We know the *current* devicetree describes the offset
> correctly, but there may be other devicetrees that do not describe it,
> and we need to keep .cpu_addr_fixup() for those other devicetrees.
>
> So there's nothing the current user can or should do about this.

Okay

Frank
>
> > +				 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) {
> > +		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);
> >  	return cpu_phy_addr - reg_addr;
> >  }