linux-kernel - [PATCH 3/4] PCI: dwc: Look up 'config' address

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Message-Id: <20250307233744.440476-4-helgaas@kernel.org>
Date: Fri,  7 Mar 2025 17:37:43 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Frank Li <Frank.Li@....com>
Cc: Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Niklas Cassel <cassel@...nel.org>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: [PATCH 3/4] PCI: dwc: Look up 'config' address

From: Bjorn Helgaas <bhelgaas@...gle.com>

Set pp->parent_bus_offset based on the parent bus address from the "config"
reg entry if it exists.

.cpu_addr_fixup(res->start) (if implemented) should return the parent bus
address corresponding to res->start.

Sets pp->parent_bus_offset, but doesn't use it, so no functional change
intended yet.
---
 .../pci/controller/dwc/pcie-designware-host.c | 42 +++++++++++++++++++
 drivers/pci/controller/dwc/pcie-designware.h  |  1 +
 2 files changed, 43 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index b9eaba157dae..e22f650ada5a 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -423,7 +423,11 @@ static int dw_pcie_cfg0_setup(struct dw_pcie_rp *pp)
 	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
 	struct device *dev = pci->dev;
 	struct platform_device *pdev = to_platform_device(dev);
+	struct device_node *np = dev->of_node;
 	struct resource *res;
+	int index;
+	u64 reg_addr, fixup_addr;
+	u64 (*fixup)(struct dw_pcie *pcie, u64 cpu_addr);
 
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "config");
 	if (!res) {
@@ -434,6 +438,44 @@ static int dw_pcie_cfg0_setup(struct dw_pcie_rp *pp)
 	pp->cfg0_size = resource_size(res);
 	pp->cfg0_base = res->start;
 
+	/* [mem 0x7ff00000-] in example */
+	dev_info(dev, "%pR config CPU physical\n", res);
+
+	/* Look up "config" address on parent bus */
+	reg_addr = 0;
+	index = of_property_match_string(np, "reg-names", "config");
+	if (index >= 0) {
+		of_property_read_reg(np, index, &reg_addr, NULL);
+		/* [ia  0x8ff00000-] in example */
+		dev_info(dev, "%#010llx config reg[%d] parent bus addr\n",
+			 reg_addr, index);
+	} else {
+		reg_addr = res->start;
+		dev_warn(dev, "%#010llx assumed parent bus addr (no config reg-names entry)\n",
+			 reg_addr);
+	}
+
+	fixup = pci->ops->cpu_addr_fixup;
+	if (fixup) {
+		fixup_addr = fixup(pci, res->start);
+		dev_info(dev, "%#010llx result of %ps(%#010llx)\n",
+			 fixup_addr, fixup, res->start);
+		if (reg_addr == fixup_addr) {
+			dev_info(dev, "%#010llx config reg[%d] == %#010llx; %ps is redundant\n",
+				 reg_addr, index, fixup_addr, fixup);
+		} else {
+			dev_warn(dev, "%#010llx config reg[%d] != %#010llx fixed up addr; DT is broken\n",
+				 reg_addr, index, fixup_addr);
+			reg_addr = fixup_addr;
+		}
+	}
+
+	/* 0x7ff00000 - 0x8ff00000 == 0xf0000000 */
+	pp->parent_bus_offset = res->start - reg_addr;
+	dev_info(dev, "%#010llx config parent bus offset\n",
+		 pp->parent_bus_offset);
+
+
 	pp->va_cfg0_base = devm_pci_remap_cfg_resource(dev, res);
 	if (IS_ERR(pp->va_cfg0_base))
 		return PTR_ERR(pp->va_cfg0_base);
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index ac23604c829f..eeca38ec3a2b 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -362,6 +362,7 @@ struct dw_pcie_rp {
 	u64			cfg0_base;
 	void __iomem		*va_cfg0_base;
 	u32			cfg0_size;
+	u64			parent_bus_offset;
 	resource_size_t		io_base;
 	phys_addr_t		io_bus_addr;
 	u32			io_size;
-- 
2.34.1