[PATCH 35/42] PCI: aardvark: Add support for PCI_BRIDGE_CTL_BUS_RESET on emulated bridge

[Pali Rohár]

PCI aardvark hardware supports PCIe Hot Reset via PCIE_CORE_CTRL1_REG
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. Also custom userspace script [1] which uses
setpci can trigger PCIe Hot Reset and reset the card manually.

[1] - https://alexforencich.com/wiki/en/pcie/hot-reset-linux

Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
Reviewed-by: Marek Behún <kabel@xxxxxxxxxx>
Fixes: 8a3ebd8de328 ("PCI: aardvark: Implement emulated root PCI bridge config space")
---
 drivers/pci/controller/pci-aardvark.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 13bbc0b5134d..d8fb43604154 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -558,6 +558,22 @@ advk_pci_bridge_emul_base_conf_read(struct pci_bridge_emul *bridge,
 		*value = advk_readl(pcie, PCIE_CORE_CMD_STATUS_REG);
 		return PCI_BRIDGE_EMUL_HANDLED;
 
+	case PCI_INTERRUPT_LINE: {
+		/*
+		 * From the whole 32bit register we support propagating to HW
+		 * only one bit: PCI_BRIDGE_CTL_BUS_RESET. Other bits are
+		 * retrieved only from emulated config space buffer.
+		 */
+		__le32 *cfgspace = (__le32 *)&bridge->conf;
+		u32 val = le32_to_cpu(cfgspace[PCI_INTERRUPT_LINE / 4]);
+		if (advk_readl(pcie, PCIE_CORE_CTRL1_REG) & HOT_RESET_GEN)
+			val |= PCI_BRIDGE_CTL_BUS_RESET << 16;
+		else
+			val &= ~(PCI_BRIDGE_CTL_BUS_RESET << 16);
+		*value = val;
+		return PCI_BRIDGE_EMUL_HANDLED;
+	}
+
 	default:
 		return PCI_BRIDGE_EMUL_NOT_HANDLED;
 	}
@@ -574,6 +590,17 @@ advk_pci_bridge_emul_base_conf_write(struct pci_bridge_emul *bridge,
 		advk_writel(pcie, new, PCIE_CORE_CMD_STATUS_REG);
 		break;
 
+	case PCI_INTERRUPT_LINE:
+		if (mask & (PCI_BRIDGE_CTL_BUS_RESET << 16)) {
+			u32 val = advk_readl(pcie, PCIE_CORE_CTRL1_REG);
+			if (new & (PCI_BRIDGE_CTL_BUS_RESET << 16))
+				val |= HOT_RESET_GEN;
+			else
+				val &= ~HOT_RESET_GEN;
+			advk_writel(pcie, val, PCIE_CORE_CTRL1_REG);
+		}
+		break;
+
 	default:
 		break;
 	}
-- 
2.20.1