From fad214b0aa726ee21adcac4308d388efcb89d6bd Mon Sep 17 00:00:00 2001 From: Mayurkumar Patel Date: Thu, 8 Sep 2016 15:07:56 -0500 Subject: [PATCH] PCI: pciehp: Process all hotplug events before looking for new ones Previously we accumulated hotplug events, then processed them, essentially like this: events = 0 do { status = read(Slot Status) status &= EVENT_MASK # only look at events events |= status # accumulate events write(Slot Status, events) # clear events } while (status) process events The problem is that as soon as we clear events in Slot Status, the hardware may send notifications for new events, and we lose information about the first events. For example, we might see two Presence Detect Changed events, but lose the fact that the slot was temporarily empty: read PCI_EXP_SLTSTA_PDC set, PCI_EXP_SLTSTA_PDS clear # slot empty write PCI_EXP_SLTSTA_PDC # clear PDC event read PCI_EXP_SLTSTA_PDC set, PCI_EXP_SLTSTA_PDS set # slot occupied The current code does not process a removal; it only processes the insertion, which fails because we didn't remove the original device. To avoid this problem, read Slot Status once and process all the events before reading it again, like this: do { read events clear events process events } while (events) [bhelgaas: changelog, add external loop around pciehp_isr()] Tested-by: Lukas Wunner Signed-off-by: Mayurkumar Patel Signed-off-by: Bjorn Helgaas Reviewed-by: Mika Westerberg --- drivers/pci/hotplug/pciehp_hpc.c | 58 ++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 26 deletions(-) diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c index b8efe1bbc4f4..625fa6a2f3ab 100644 --- a/drivers/pci/hotplug/pciehp_hpc.c +++ b/drivers/pci/hotplug/pciehp_hpc.c @@ -535,7 +535,7 @@ void pciehp_power_off_slot(struct slot *slot) PCI_EXP_SLTCTL_PWR_OFF); } -static irqreturn_t pcie_isr(int irq, void *dev_id) +static irqreturn_t pciehp_isr(int irq, void *dev_id) { struct controller *ctrl = (struct controller *)dev_id; struct pci_dev *pdev = ctrl_dev(ctrl); @@ -550,36 +550,23 @@ static irqreturn_t pcie_isr(int irq, void *dev_id) if (pdev->current_state == PCI_D3cold) return IRQ_NONE; + pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status); + if (status == (u16) ~0) { + ctrl_info(ctrl, "%s: no response from device\n", __func__); + return IRQ_NONE; + } + /* - * In order to guarantee that all interrupt events are - * serviced, we need to re-inspect Slot Status register after - * clearing what is presumed to be the last pending interrupt. + * Slot Status contains plain status bits as well as event + * notification bits; right now we only want the event bits. */ - events = 0; - do { - pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &status); - if (status == (u16) ~0) { - ctrl_info(ctrl, "%s: no response from device\n", - __func__); - return IRQ_NONE; - } - - /* - * Slot Status contains plain status bits as well as event - * notification bits; right now we only want the event bits. - */ - status &= (PCI_EXP_SLTSTA_ABP | PCI_EXP_SLTSTA_PFD | + events = status & (PCI_EXP_SLTSTA_ABP | PCI_EXP_SLTSTA_PFD | PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_CC | PCI_EXP_SLTSTA_DLLSC); - status &= ~events; - events |= status; - if (!events) - return IRQ_NONE; - if (status) - pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, - events); - } while (status); + if (!events) + return IRQ_NONE; + pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, events); ctrl_dbg(ctrl, "pending interrupts %#06x from Slot Status\n", events); /* Check Command Complete Interrupt Pending */ @@ -636,6 +623,25 @@ static irqreturn_t pcie_isr(int irq, void *dev_id) return IRQ_HANDLED; } +static irqreturn_t pcie_isr(int irq, void *dev_id) +{ + irqreturn_t rc, handled = IRQ_NONE; + + /* + * To guarantee that all interrupt events are serviced, we need to + * re-inspect Slot Status register after clearing what is presumed + * to be the last pending interrupt. + */ + do { + rc = pciehp_isr(irq, dev_id); + if (rc == IRQ_HANDLED) + handled = IRQ_HANDLED; + } while (rc == IRQ_HANDLED); + + /* Return IRQ_HANDLED if we handled one or more events */ + return handled; +} + void pcie_enable_notification(struct controller *ctrl) { u16 cmd, mask; -- 2.20.1