PCI: mvebu: Fix support for PCI_BRIDGE_CTL_BUS_RESET on emulated bridge

Hardware supports PCIe Hot Reset via PCIE_CTRL_OFF register. Use it for
implementing PCI_BRIDGE_CTL_BUS_RESET bit of PCI_BRIDGE_CONTROL register on
emulated bridge.

With this change the function pci_reset_secondary_bus() starts working and
can reset connected PCIe card.

Link: https://lore.kernel.org/r/20211125124605.25915-13-pali@kernel.org
Fixes: 1f08673 ("PCI: mvebu: Convert to PCI emulated bridge config space")
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Author: pali

drivers/pci/controller/pci-mvebu.c

@@ -56,6 +56,7 @@
 #define PCIE_CTRL_OFF		0x1a00
 #define  PCIE_CTRL_X1_MODE		0x0001
 #define  PCIE_CTRL_RC_MODE		BIT(1)
+#define  PCIE_CTRL_MASTER_HOT_RESET	BIT(24)
 #define PCIE_STAT_OFF		0x1a04
 #define  PCIE_STAT_BUS                  0xff00
 #define  PCIE_STAT_DEV                  0x1f0000
@@ -498,6 +499,22 @@ mvebu_pci_bridge_emul_base_conf_read(struct pci_bridge_emul *bridge,
 		break;
 	}
 
+	case PCI_INTERRUPT_LINE: {
+		/*
+		 * From the whole 32bit register we support reading from HW only
+		 * one bit: PCI_BRIDGE_CTL_BUS_RESET.
+		 * Other bits are retrieved only from emulated config buffer.
+		 */
+		__le32 *cfgspace = (__le32 *)&bridge->conf;
+		u32 val = le32_to_cpu(cfgspace[PCI_INTERRUPT_LINE / 4]);
+		if (mvebu_readl(port, PCIE_CTRL_OFF) & PCIE_CTRL_MASTER_HOT_RESET)
+			val |= PCI_BRIDGE_CTL_BUS_RESET << 16;
+		else
+			val &= ~(PCI_BRIDGE_CTL_BUS_RESET << 16);
+		*value = val;
+		break;
+	}
+
 	default:
 		return PCI_BRIDGE_EMUL_NOT_HANDLED;
 	}
@@ -606,6 +623,17 @@ mvebu_pci_bridge_emul_base_conf_write(struct pci_bridge_emul *bridge,
 			mvebu_pcie_set_local_bus_nr(port, conf->secondary_bus);
 		break;
 
+	case PCI_INTERRUPT_LINE:
+		if (mask & (PCI_BRIDGE_CTL_BUS_RESET << 16)) {
+			u32 ctrl = mvebu_readl(port, PCIE_CTRL_OFF);
+			if (new & (PCI_BRIDGE_CTL_BUS_RESET << 16))
+				ctrl |= PCIE_CTRL_MASTER_HOT_RESET;
+			else
+				ctrl &= ~PCIE_CTRL_MASTER_HOT_RESET;
+			mvebu_writel(port, ctrl, PCIE_CTRL_OFF);
+		}
+		break;
+
 	default:
 		break;
 	}