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Subject[PATCH] PCI/LINK: bw_notification: Do not leave interrupt handler NULL
Date
A threaded IRQ with a NULL handler does not work with level-triggered
interrupts. request_threaded_irq() will return an error:

genirq: Threaded irq requested with handler=NULL and !ONESHOT for irq 16
pcie_bw_notification: probe of 0000:00:1b.0:pcie010 failed with error -22

For level interrupts we need to silence the interrupt before exiting
the IRQ handler, so just clear the PCI_EXP_LNKSTA_LBMS bit there.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
---

OOPS! I'm sorry for the noise. Here's the fix.

I was able to test this on edge-triggered interrupts. None of my
machines have PCIe ports that use level-triggered interrupts. This
might not be too straightforward to test without a hardware yanker,
but if there's a way to force a specific interrupt to be level
triggered, I could do the testing on my end.

drivers/pci/pcie/bw_notification.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/pcie/bw_notification.c b/drivers/pci/pcie/bw_notification.c
index d2eae3b7cc0f..001d6253ad48 100644
--- a/drivers/pci/pcie/bw_notification.c
+++ b/drivers/pci/pcie/bw_notification.c
@@ -44,11 +44,10 @@ static void pcie_disable_link_bandwidth_notification(struct pci_dev *dev)
pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
}

-static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
+static irqreturn_t pcie_bw_notification_irq(int irq, void *context)
{
struct pcie_device *srv = context;
struct pci_dev *port = srv->port;
- struct pci_dev *dev;
u16 link_status, events;
int ret;

@@ -58,6 +57,17 @@ static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
if (ret != PCIBIOS_SUCCESSFUL || !events)
return IRQ_NONE;

+ pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
+ return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
+{
+ struct pcie_device *srv = context;
+ struct pci_dev *port = srv->port;
+ struct pci_dev *dev;
+ u16 link_status;
+
/*
* Print status from downstream devices, not this root port or
* downstream switch port.
@@ -67,8 +77,8 @@ static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
__pcie_print_link_status(dev, false);
up_read(&pci_bus_sem);

+ pcie_capability_read_word(port, PCI_EXP_LNKSTA, &link_status);
pcie_update_link_speed(port->subordinate, link_status);
- pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
return IRQ_HANDLED;
}

@@ -80,7 +90,8 @@ static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
if (!pcie_link_bandwidth_notification_supported(srv->port))
return -ENODEV;

- ret = request_threaded_irq(srv->irq, NULL, pcie_bw_notification_handler,
+ ret = request_threaded_irq(srv->irq, pcie_bw_notification_irq,
+ pcie_bw_notification_handler,
IRQF_SHARED, "PCIe BW notif", srv);
if (ret)
return ret;
--
2.19.2
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