[PATCH 5.16 0806/1039] PCI: mvebu: Fix support for PCI_EXP_RTSTA on emulated bridge

[Greg Kroah-Hartman]

From: Pali Rohár <pali@xxxxxxxxxx>

[ Upstream commit 838ff44a398ff47fe9b924961d91aee325821220 ]

PME Status bit in Root Status Register (PCIE_RC_RTSTA_OFF) is read-only and
can be cleared only by writing 0b to the Interrupt Cause RW0C register
(PCIE_INT_CAUSE_OFF).

Link: https://lore.kernel.org/r/20211125124605.25915-15-pali@xxxxxxxxxx
Fixes: 1f08673eef12 ("PCI: mvebu: Convert to PCI emulated bridge config space")
Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/pci/controller/pci-mvebu.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
index 0052e83c95de9..618c34e8879ec 100644
--- a/drivers/pci/controller/pci-mvebu.c
+++ b/drivers/pci/controller/pci-mvebu.c
@@ -51,6 +51,8 @@
 	 PCIE_CONF_FUNC(PCI_FUNC(devfn)) | PCIE_CONF_REG(where) | \
 	 PCIE_CONF_ADDR_EN)
 #define PCIE_CONF_DATA_OFF	0x18fc
+#define PCIE_INT_CAUSE_OFF	0x1900
+#define  PCIE_INT_PM_PME		BIT(28)
 #define PCIE_MASK_OFF		0x1910
 #define  PCIE_MASK_ENABLE_INTS          0x0f000000
 #define PCIE_CTRL_OFF		0x1a00
@@ -604,7 +606,14 @@ mvebu_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
 		break;
 
 	case PCI_EXP_RTSTA:
-		mvebu_writel(port, new, PCIE_RC_RTSTA);
+		/*
+		 * PME Status bit in Root Status Register (PCIE_RC_RTSTA)
+		 * is read-only and can be cleared only by writing 0b to the
+		 * Interrupt Cause RW0C register (PCIE_INT_CAUSE_OFF). So
+		 * clear PME via Interrupt Cause.
+		 */
+		if (new & PCI_EXP_RTSTA_PME)
+			mvebu_writel(port, ~PCIE_INT_PM_PME, PCIE_INT_CAUSE_OFF);
 		break;
 	}
 }
-- 
2.34.1