PCI: mediatek-gen3: Configure PBUS_CSR registers for EN7581 SoC

Configure PBus base address and address mask to allow the hw
to detect if a given address is accessible on PCIe controller.

Fixes: f6ab898 ("PCI: mediatek-gen3: Add Airoha EN7581 support")
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://lore.kernel.org/r/20250225-en7581-pcie-pbus-csr-v4-2-24324382424a@kernel.org
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

Author: LorenzoBianconi

drivers/pci/controller/pcie-mediatek-gen3.c

@@ -15,6 +15,7 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/msi.h>
 #include <linux/of_device.h>
@@ -24,6 +25,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_domain.h>
 #include <linux/pm_runtime.h>
+#include <linux/regmap.h>
 #include <linux/reset.h>
 
 #include "../pci.h"
@@ -930,9 +932,13 @@ static int mtk_pcie_parse_port(struct mtk_gen3_pcie *pcie)
 
 static int mtk_pcie_en7581_power_up(struct mtk_gen3_pcie *pcie)
 {
+	struct pci_host_bridge *host = pci_host_bridge_from_priv(pcie);
 	struct device *dev = pcie->dev;
+	struct resource_entry *entry;
+	struct regmap *pbus_regmap;
+	u32 val, args[2], size;
+	resource_size_t addr;
 	int err;
-	u32 val;
 
 	/*
 	 * The controller may have been left out of reset by the bootloader
@@ -944,6 +950,26 @@ static int mtk_pcie_en7581_power_up(struct mtk_gen3_pcie *pcie)
 	/* Wait for the time needed to complete the reset lines assert. */
 	msleep(PCIE_EN7581_RESET_TIME_MS);
 
+	/*
+	 * Configure PBus base address and base address mask to allow the
+	 * hw to detect if a given address is accessible on PCIe controller.
+	 */
+	pbus_regmap = syscon_regmap_lookup_by_phandle_args(dev->of_node,
+							   "mediatek,pbus-csr",
+							   ARRAY_SIZE(args),
+							   args);
+	if (IS_ERR(pbus_regmap))
+		return PTR_ERR(pbus_regmap);
+
+	entry = resource_list_first_type(&host->windows, IORESOURCE_MEM);
+	if (!entry)
+		return -ENODEV;
+
+	addr = entry->res->start - entry->offset;
+	regmap_write(pbus_regmap, args[0], lower_32_bits(addr));
+	size = lower_32_bits(resource_size(entry->res));
+	regmap_write(pbus_regmap, args[1], GENMASK(31, __fls(size)));
+
 	/*
 	 * Unlike the other MediaTek Gen3 controllers, the Airoha EN7581
 	 * requires PHY initialization and power-on before PHY reset deassert.