[RFC PATCH 10/12] usb: xhci: add interrupter type

[Niklas Neronin <niklas.neronin@linux.intel.com>]

xhci-sideband creates a secondary interrupter without an associated IRQ.
Such interrupters are non-operational and cannot enabled or disabled.

Add a type field to struct 'xhci_interrupter' to distinguish
non-operational interrupters. When the type is set to 'INTR_NOOP',
the interrupter enable/disable helpers become no-ops.

This allows callers to iterate over all allocated interrupters without
special-casing, while ensuring that actions are applied only to operational
interrupters. It also provides a simple extension point for adding
additional interrupter types in the future.

Operational interrupters remain the default; no-op interrupters are the
exception.

No functional changes are introduced; behavior remains the same.

This change is necessary to prepare the driver for multiple interrupters.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
---
 drivers/usb/host/xhci-sideband.c | 1 +
 drivers/usb/host/xhci.c          | 6 ++++++
 drivers/usb/host/xhci.h          | 8 ++++++++
 3 files changed, 15 insertions(+)

diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
index 2bd77255032b..21ee4e96bc70 100644
--- a/drivers/usb/host/xhci-sideband.c
+++ b/drivers/usb/host/xhci-sideband.c
@@ -352,6 +352,7 @@ xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
 	ret = usb_offload_get(udev);
 
 	sb->ir->ip_autoclear = ip_autoclear;
+	sb->ir->type = INTR_NOOP;
 
 	return ret;
 }
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index e03f717d2314..329fe9ff19f8 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -317,6 +317,9 @@ int xhci_enable_interrupter(struct xhci_interrupter *ir)
 	if (!ir || !ir->ir_set)
 		return -EINVAL;
 
+	if (ir->type == INTR_NOOP)
+		return 0;
+
 	iman = readl(&ir->ir_set->iman);
 	iman &= ~IMAN_IP;
 	iman |= IMAN_IE;
@@ -334,6 +337,9 @@ int xhci_disable_interrupter(struct xhci_hcd *xhci, struct xhci_interrupter *ir)
 	if (!ir || !ir->ir_set)
 		return -EINVAL;
 
+	if (ir->type == INTR_NOOP)
+		return 0;
+
 	iman = readl(&ir->ir_set->iman);
 	iman &= ~IMAN_IP;
 	iman &= ~IMAN_IE;
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index e6a51f1318c2..1e9ea6507813 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1443,6 +1443,13 @@ struct xhci_bus_state {
 	unsigned long		resuming_ports;
 };
 
+enum interrupter_type {
+	/* Normal interrupter, e.g. Primary */
+	INTR_DEFAULT,
+	/* Non-operational, e.g. xhci-sideband */
+	INTR_NOOP,
+};
+
 struct xhci_interrupter {
 	struct xhci_ring	*event_ring;
 	struct xhci_erst	erst;
@@ -1450,6 +1457,7 @@ struct xhci_interrupter {
 	unsigned int		intr_num;
 	bool			ip_autoclear;
 	u32			isoc_bei_interval;
+	enum interrupter_type	type;
 	/* For interrupter registers save and restore over suspend/resume */
 	u32	s3_iman;
 	u32	s3_imod;
-- 
2.50.1