| Message ID | 20180209120415.17590-2-vigneshr@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Fri, Feb 09, 2018 at 05:34:13PM +0530, Vignesh R wrote: > Since commit 06e15e6883bed ("PCI: dwc: Clear MSI interrupt status after > it is handled, not before"), MSI IRQ status in PCIE_MSI_INTR0_STATUS > register is cleared after calling EP's IRQ handler. Small nit, the SHA1 is actually: 8c934095fa2f ("PCI: dwc: Clear MSI interrupt status after it is handled, not before") Acked-by: Niklas Cassel <niklas.cassel@axis.com>
diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c index 8de2d5c69b1d..c29cbcd430f4 100644 --- a/drivers/pci/dwc/pcie-designware-host.c +++ b/drivers/pci/dwc/pcie-designware-host.c @@ -68,9 +68,9 @@ irqreturn_t dw_handle_msi_irq(struct pcie_port *pp) while ((pos = find_next_bit((unsigned long *) &val, 32, pos)) != 32) { irq = irq_find_mapping(pp->irq_domain, i * 32 + pos); - generic_handle_irq(irq); dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_STATUS + i * 12, 4, 1 << pos); + generic_handle_irq(irq); pos++; } }
Since commit 06e15e6883bed ("PCI: dwc: Clear MSI interrupt status after it is handled, not before"), MSI IRQ status in PCIE_MSI_INTR0_STATUS register is cleared after calling EP's IRQ handler. But, MSI IRQs in case of PCIe are bit like edge interrupts. If a another MSI IRQ is raised and the end of current EP's IRQ handler call but before clearing the MSI IRQ status in PCIE_MSI_INTR0_STATUS register then the new MSI IRQ is lost. This issue has been observed in case of USB-Ethernet adapter connected to PCIe USB card running iperf3 test. iperf3 client stalls after sometime as reported here[1]. This is because XHCI raises MSI IRQ at the end of its IRQ handler but before PCIe driver has cleared its status in PCIE_MSI_INTR0_STATUS register. Hence, the new IRQ is never registered by PCIe designware core. Since, XHCI does not raise any more IRQs until the previous one is handled, it leads to a stall in communication. Therefore driver should always clear the MSI IRQ status in PCIE_MSI_INTR0_STATUS before calling EP's IRQ handler. This make sure that DW PCIe core catches new IRQ raised during the call to EP's IRQ handler [1] https://lkml.kernel.org/r/BN6PR18MB124994D85EAC4B5B1AD5EC56866E0@BN6PR18MB1249.namprd18.prod.outlook.com Signed-off-by: Vignesh R <vigneshr@ti.com> --- drivers/pci/dwc/pcie-designware-host.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)