[PATCH Zesty SRU] drivers/pci/hotplug: Mask PDC interrupt if required

[Tim Gardner]

From: Gavin Shan <gwshan at linux.vnet.ibm.com>

BugLink: http://bugs.launchpad.net/bugs/1680328

We're supporting surprise hotplug on PCI slots behind root port
or PCIe switch downstream ports, which don't claim the capability
in hardware register (offset: PCIe cap + PCI_EXP_SLTCAP). PEX8718
is one of the examples. For those PCI slots, the PDC (Presence
Detection Change) event isn't reliable and the underly (skiboot)
firmware has best judgement.

This masks the PDC event when skiboot requests by "ibm,slot-broken-pdc"
property in PCI slot's device-tree node.

Reported-by: Hank Chang <hankmax0000 at gmail.com>
Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
Tested-by: Willie Liauw <williel at supermicro.com.tw>
Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
(cherry picked from commit 454593e54cac126a0f49d4b65f90a5e518c51404)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 arch/powerpc/include/asm/pnv-pci.h |  2 ++
 drivers/pci/hotplug/pnv_php.c      | 27 ++++++++++++++++++++++-----
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/pnv-pci.h b/arch/powerpc/include/asm/pnv-pci.h
index 696438f..de96810 100644
--- a/arch/powerpc/include/asm/pnv-pci.h
+++ b/arch/powerpc/include/asm/pnv-pci.h
@@ -57,6 +57,8 @@ struct pnv_php_slot {
 	uint64_t			id;
 	char				*name;
 	int				slot_no;
+	unsigned int			flags;
+#define PNV_PHP_FLAG_BROKEN_PDC		0x1
 	struct kref			kref;
 #define PNV_PHP_STATE_INITIALIZED	0
 #define PNV_PHP_STATE_REGISTERED	1
diff --git a/drivers/pci/hotplug/pnv_php.c b/drivers/pci/hotplug/pnv_php.c
index e96973b..335a556 100644
--- a/drivers/pci/hotplug/pnv_php.c
+++ b/drivers/pci/hotplug/pnv_php.c
@@ -723,7 +723,8 @@ static irqreturn_t pnv_php_interrupt(int irq, void *data)
 	if (sts & PCI_EXP_SLTSTA_DLLSC) {
 		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lsts);
 		added = !!(lsts & PCI_EXP_LNKSTA_DLLLA);
-	} else if (sts & PCI_EXP_SLTSTA_PDC) {
+	} else if (!(php_slot->flags & PNV_PHP_FLAG_BROKEN_PDC) &&
+		   (sts & PCI_EXP_SLTSTA_PDC)) {
 		ret = pnv_pci_get_presence_state(php_slot->id, &presence);
 		if (ret) {
 			dev_warn(&pdev->dev, "PCI slot [%s] error %d getting presence (0x%04x), to retry the operation.\n",
@@ -774,6 +775,7 @@ static irqreturn_t pnv_php_interrupt(int irq, void *data)
 static void pnv_php_init_irq(struct pnv_php_slot *php_slot, int irq)
 {
 	struct pci_dev *pdev = php_slot->pdev;
+	u32 broken_pdc = 0;
 	u16 sts, ctrl;
 	int ret;
 
@@ -785,9 +787,18 @@ static void pnv_php_init_irq(struct pnv_php_slot *php_slot, int irq)
 		return;
 	}
 
+	/* Check PDC (Presence Detection Change) is broken or not */
+	ret = of_property_read_u32(php_slot->dn, "ibm,slot-broken-pdc",
+				   &broken_pdc);
+	if (!ret && broken_pdc)
+		php_slot->flags |= PNV_PHP_FLAG_BROKEN_PDC;
+
 	/* Clear pending interrupts */
 	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &sts);
-	sts |= (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC);
+	if (php_slot->flags & PNV_PHP_FLAG_BROKEN_PDC)
+		sts |= PCI_EXP_SLTSTA_DLLSC;
+	else
+		sts |= (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC);
 	pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, sts);
 
 	/* Request the interrupt */
@@ -801,9 +812,15 @@ static void pnv_php_init_irq(struct pnv_php_slot *php_slot, int irq)
 
 	/* Enable the interrupts */
 	pcie_capability_read_word(pdev, PCI_EXP_SLTCTL, &ctrl);
-	ctrl |= (PCI_EXP_SLTCTL_HPIE |
-		 PCI_EXP_SLTCTL_PDCE |
-		 PCI_EXP_SLTCTL_DLLSCE);
+	if (php_slot->flags & PNV_PHP_FLAG_BROKEN_PDC) {
+		ctrl &= ~PCI_EXP_SLTCTL_PDCE;
+		ctrl |= (PCI_EXP_SLTCTL_HPIE |
+			 PCI_EXP_SLTCTL_DLLSCE);
+	} else {
+		ctrl |= (PCI_EXP_SLTCTL_HPIE |
+			 PCI_EXP_SLTCTL_PDCE |
+			 PCI_EXP_SLTCTL_DLLSCE);
+	}
 	pcie_capability_write_word(pdev, PCI_EXP_SLTCTL, ctrl);
 
 	/* The interrupt is initialized successfully when @irq is valid */
-- 
2.7.4