PCI: dw-rockchip: Enumerate endpoints based on dll_link_up IRQ

Most boards using the pcie-dw-rockchip PCIe controller lack standard
hotplug support.

Thus, when an endpoint is attached to the SoC, users have to rescan the bus
manually to enumerate the device. This can be avoided by using the
'dll_link_up' interrupt in the combined system interrupt 'sys'.

Once the 'dll_link_up' IRQ is received, the bus underneath the host bridge
is scanned to enumerate PCIe endpoint devices.

This implements the same functionality that was implemented in the DWC
based pcie-qcom driver in 4581403 ("PCI: qcom: Enumerate endpoints
based on Link up event in 'global_irq' interrupt").

The Root Complex specific device tree binding for pcie-dw-rockchip already
has the 'sys' interrupt marked as required, so there is no need to update
the device tree binding. This also means that we can request the 'sys' IRQ
unconditionally.

Link: https://lore.kernel.org/r/20241127145041.3531400-2-cassel@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
[bhelgaas: commit log, squash Pei Xiao's redundant dev_err() fix from
https://lore.kernel.org/r/327718207d3cd72847c079ff9d56eb246744c182.1736126067.git.xiaopei01@kylinos.cn,
squash Niklas's #define change from https://lore.kernel.org/r/20250103095812.2408364-2-cassel@kernel.org]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Author: floatious

drivers/pci/controller/dwc/pcie-dw-rockchip.c

@@ -389,6 +389,34 @@ static const struct dw_pcie_ops dw_pcie_ops = {
 	.stop_link = rockchip_pcie_stop_link,
 };
 
+static irqreturn_t rockchip_pcie_rc_sys_irq_thread(int irq, void *arg)
+{
+	struct rockchip_pcie *rockchip = arg;
+	struct dw_pcie *pci = &rockchip->pci;
+	struct dw_pcie_rp *pp = &pci->pp;
+	struct device *dev = pci->dev;
+	u32 reg, val;
+
+	reg = rockchip_pcie_readl_apb(rockchip, PCIE_CLIENT_INTR_STATUS_MISC);
+	rockchip_pcie_writel_apb(rockchip, reg, PCIE_CLIENT_INTR_STATUS_MISC);
+
+	dev_dbg(dev, "PCIE_CLIENT_INTR_STATUS_MISC: %#x\n", reg);
+	dev_dbg(dev, "LTSSM_STATUS: %#x\n", rockchip_pcie_get_ltssm(rockchip));
+
+	if (reg & PCIE_RDLH_LINK_UP_CHGED) {
+		val = rockchip_pcie_get_ltssm(rockchip);
+		if ((val & PCIE_LINKUP) == PCIE_LINKUP) {
+			dev_dbg(dev, "Received Link up event. Starting enumeration!\n");
+			/* Rescan the bus to enumerate endpoint devices */
+			pci_lock_rescan_remove();
+			pci_rescan_bus(pp->bridge->bus);
+			pci_unlock_rescan_remove();
+		}
+	}
+
+	return IRQ_HANDLED;
+}
+
 static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
 {
 	struct rockchip_pcie *rockchip = arg;
@@ -418,14 +446,29 @@ static irqreturn_t rockchip_pcie_ep_sys_irq_thread(int irq, void *arg)
 	return IRQ_HANDLED;
 }
 
-static int rockchip_pcie_configure_rc(struct rockchip_pcie *rockchip)
+static int rockchip_pcie_configure_rc(struct platform_device *pdev,
+				      struct rockchip_pcie *rockchip)
 {
+	struct device *dev = &pdev->dev;
 	struct dw_pcie_rp *pp;
+	int irq, ret;
 	u32 val;
 
 	if (!IS_ENABLED(CONFIG_PCIE_ROCKCHIP_DW_HOST))
 		return -ENODEV;
 
+	irq = platform_get_irq_byname(pdev, "sys");
+	if (irq < 0)
+		return irq;
+
+	ret = devm_request_threaded_irq(dev, irq, NULL,
+					rockchip_pcie_rc_sys_irq_thread,
+					IRQF_ONESHOT, "pcie-sys-rc", rockchip);
+	if (ret) {
+		dev_err(dev, "failed to request PCIe sys IRQ\n");
+		return ret;
+	}
+
 	/* LTSSM enable control mode */
 	val = HIWORD_UPDATE_BIT(PCIE_LTSSM_ENABLE_ENHANCE);
 	rockchip_pcie_writel_apb(rockchip, val, PCIE_CLIENT_HOT_RESET_CTRL);
@@ -436,7 +479,17 @@ static int rockchip_pcie_configure_rc(struct rockchip_pcie *rockchip)
 	pp = &rockchip->pci.pp;
 	pp->ops = &rockchip_pcie_host_ops;
 
-	return dw_pcie_host_init(pp);
+	ret = dw_pcie_host_init(pp);
+	if (ret) {
+		dev_err(dev, "failed to initialize host\n");
+		return ret;
+	}
+
+	/* unmask DLL up/down indicator */
+	val = HIWORD_UPDATE(PCIE_RDLH_LINK_UP_CHGED, 0);
+	rockchip_pcie_writel_apb(rockchip, val, PCIE_CLIENT_INTR_MASK_MISC);
+
+	return ret;
 }
 
 static int rockchip_pcie_configure_ep(struct platform_device *pdev,
@@ -450,14 +503,12 @@ static int rockchip_pcie_configure_ep(struct platform_device *pdev,
 		return -ENODEV;
 
 	irq = platform_get_irq_byname(pdev, "sys");
-	if (irq < 0) {
-		dev_err(dev, "missing sys IRQ resource\n");
+	if (irq < 0)
 		return irq;
-	}
 
 	ret = devm_request_threaded_irq(dev, irq, NULL,
 					rockchip_pcie_ep_sys_irq_thread,
-					IRQF_ONESHOT, "pcie-sys", rockchip);
+					IRQF_ONESHOT, "pcie-sys-ep", rockchip);
 	if (ret) {
 		dev_err(dev, "failed to request PCIe sys IRQ\n");
 		return ret;
@@ -491,7 +542,8 @@ static int rockchip_pcie_configure_ep(struct platform_device *pdev,
 	pci_epc_init_notify(rockchip->pci.ep.epc);
 
 	/* unmask DLL up/down indicator and hot reset/link-down reset */
-	rockchip_pcie_writel_apb(rockchip, 0x60000, PCIE_CLIENT_INTR_MASK_MISC);
+	val = HIWORD_UPDATE(PCIE_RDLH_LINK_UP_CHGED | PCIE_LINK_REQ_RST_NOT_INT, 0);
+	rockchip_pcie_writel_apb(rockchip, val, PCIE_CLIENT_INTR_MASK_MISC);
 
 	return ret;
 }
@@ -553,7 +605,7 @@ static int rockchip_pcie_probe(struct platform_device *pdev)
 
 	switch (data->mode) {
 	case DW_PCIE_RC_TYPE:
-		ret = rockchip_pcie_configure_rc(rockchip);
+		ret = rockchip_pcie_configure_rc(pdev, rockchip);
 		if (ret)
 			goto deinit_clk;
 		break;