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

[Bjorn Helgaas <helgaas@kernel.org>]

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) {
+		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;
 }
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 16548b01347d..f08d2852cfd5 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/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)
-- 
2.34.1