From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lelnx194.ext.ti.com ([198.47.27.80]:29054 "EHLO lelnx194.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751007AbeBIMDx (ORCPT ); Fri, 9 Feb 2018 07:03:53 -0500 From: Vignesh R To: Lorenzo Pieralisi , Jingoo Han , Joao Pinto CC: Kishon Vijay Abraham I , Bjorn Helgaas , Niklas Cassel , , , , Vignesh R Subject: [PATCH 1/3] Revert "PCI: dwc: Clear MSI interrupt status after it is handled, not before" Date: Fri, 9 Feb 2018 17:34:13 +0530 Message-ID: <20180209120415.17590-2-vigneshr@ti.com> In-Reply-To: <20180209120415.17590-1-vigneshr@ti.com> References: <20180209120415.17590-1-vigneshr@ti.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-pci-owner@vger.kernel.org List-ID: 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 --- drivers/pci/dwc/pcie-designware-host.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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++; } } -- 2.16.1