PCI: dwc: Add dw_pcie_parent_bus_offset() checking and debug

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/20250315201548.858189-7-helgaas@kernel.org
Signed-off-by: Frank Li <Frank.Li@nxp.com>
[bhelgaas: squash Ioana Ciornei <ioana.ciornei@nxp.com> fix for NULL
pointer deref when driver doesn't supply dw_pcie_ops, e.g., layerscape-pcie
https://lore.kernel.org/r/20250319134339.3114817-1-ioana.ciornei@nxp.com]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: nxpfrankli

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 +1127,42 @@ resource_size_t dw_pcie_parent_bus_offset(struct dw_pcie *pci,
 
 	of_property_read_reg(np, index, &reg_addr, NULL);
 
+	fixup = pci->ops ? pci->ops->cpu_addr_fixup : NULL;
+	if (fixup) {
+		fixup_addr = fixup(pci, cpu_phys_addr);
+		if (reg_addr == fixup_addr) {
+			dev_info(dev, "%s reg[%d] %#010llx == %#010llx == fixup(cpu %#010llx); %ps is redundant with this devicetree\n",
+				 reg_name, index, reg_addr, fixup_addr,
+				 (unsigned long long) cpu_phys_addr, fixup);
+		} else {
+			dev_warn(dev, "%s reg[%d] %#010llx != %#010llx == fixup(cpu %#010llx); devicetree is broken\n",
+				 reg_name, index, reg_addr, fixup_addr,
+				 (unsigned long long) cpu_phys_addr);
+			reg_addr = fixup_addr;
+		}
+
+		return cpu_phys_addr - reg_addr;
+	}
+
+	if (pci->use_parent_dt_ranges) {
+
+		/*
+		 * This platform once had a fixup, presumably because it
+		 * translates between CPU and PCI controller addresses.
+		 * Log a note if devicetree didn't describe a translation.
+		 */
+		if (reg_addr == cpu_phys_addr)
+			dev_info(dev, "%s reg[%d] %#010llx == cpu %#010llx\n; no fixup was ever needed for this devicetree\n",
+				 reg_name, index, reg_addr,
+				 (unsigned long long) cpu_phys_addr);
+	} else {
+		if (reg_addr != cpu_phys_addr) {
+			dev_warn(dev, "%s reg[%d] %#010llx != cpu %#010llx; no fixup and devicetree \"ranges\" is broken, assuming no translation\n",
+				 reg_name, index, reg_addr,
+				 (unsigned long long) cpu_phys_addr);
+			return 0;
+		}
+	}
+
 	return cpu_phys_addr - reg_addr;
 }

drivers/pci/controller/dwc/pcie-designware.h

@@ -465,6 +465,19 @@ struct dw_pcie {
 	struct reset_control_bulk_data	core_rsts[DW_PCIE_NUM_CORE_RSTS];
 	struct gpio_desc		*pe_rst;
 	bool			suspended;
+
+	/*
+	 * If iATU input addresses are offset from CPU physical addresses,
+	 * we previously required .cpu_addr_fixup() to convert them.  We
+	 * now rely on the devicetree instead.  If .cpu_addr_fixup()
+	 * exists, we compare its results with devicetree.
+	 *
+	 * If .cpu_addr_fixup() does not exist, we assume the offset is
+	 * zero and warn if devicetree claims otherwise.  If we know all
+	 * devicetrees correctly describe the offset, set
+	 * use_parent_dt_ranges to true to avoid this warning.
+	 */
+	bool			use_parent_dt_ranges;
 };
 
 #define to_dw_pcie_from_pp(port) container_of((port), struct dw_pcie, pp)