Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757405AbdLUBmt (ORCPT ); Wed, 20 Dec 2017 20:42:49 -0500 Received: from mailgw02.mediatek.com ([1.203.163.81]:5369 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756025AbdLUBmp (ORCPT ); Wed, 20 Dec 2017 20:42:45 -0500 X-Greylist: delayed 303 seconds by postgrey-1.27 at vger.kernel.org; Wed, 20 Dec 2017 20:42:44 EST X-UUID: e1b7ea9fa87045f0af1541f961970c97-20171221 Message-ID: <1513820234.25872.1.camel@mhfsdcap03> Subject: Re: [PATCH] PCI: Mediatek: clear irq status after irq dispathed to avoid reentry From: Honghui Zhang To: Bjorn Helgaas CC: , , , , , , , , , , , , , , , , Lorenzo Pieralisi Date: Thu, 21 Dec 2017 09:37:14 +0800 In-Reply-To: <20171221005240.GC30595@bhelgaas-glaptop.roam.corp.google.com> References: <1513738334-26213-1-git-send-email-honghui.zhang@mediatek.com> <20171221005240.GC30595@bhelgaas-glaptop.roam.corp.google.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3302 Lines: 90 On Wed, 2017-12-20 at 18:52 -0600, Bjorn Helgaas wrote: > [+cc Lorenzo, please cc him on all drivers/{host,dwc,endpoint} material] > > Please run "git log --oneline drivers/pci/host/pcie-mediatek.c" and > make yours match. Same capitalization, same sentence structure, etc., > e.g., > > PCI: mediatek: Clear IRQ status ... > > s/dispathed/dispatched/ > > s/irq/IRQ/ in the summary and all the English text below. Thanks for your review and sorry for the mismatch, I will fix that in next version. > > On Wed, Dec 20, 2017 at 10:52:14AM +0800, honghui.zhang@mediatek.com wrote: > > From: Honghui Zhang > > > > There maybe a same irq reentry scenario after irq received in current > > irq handle flow: > > EP device PCIe host driver EP driver > > 1. issue an irq > > 2. received irq > > 3. clear irq status > > 4. dispatch irq > > 5. clear irq source > > The irq status was not successfully cleared at step 2 since the irq > > source was not cleared yet. So the PCIe host driver may receive the > > same irq after step 5. Then there's an irq reentry occurred. > > Even worse, if the reentry irq was not an irq that EP driver expected, > > it may not handle the irq. Then we may run into the dead loop from > > By "dead loop" I assume you mean "infinite loop"? I don't think it's > a deadlock since nothing is waiting. > Yes, it should be "infinite loop", I will update the commit message in next version. thanks. > > step 2 to step 4. > > Clear the irq status after irq have been dispatched to avoid the irq > > reentry. > > > > Signed-off-by: Honghui Zhang > > --- > > drivers/pci/host/pcie-mediatek.c | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/pci/host/pcie-mediatek.c b/drivers/pci/host/pcie-mediatek.c > > index db93efd..3248771 100644 > > --- a/drivers/pci/host/pcie-mediatek.c > > +++ b/drivers/pci/host/pcie-mediatek.c > > @@ -605,11 +605,11 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data) > > > > while ((status = readl(port->base + PCIE_INT_STATUS)) & INTX_MASK) { > > for_each_set_bit_from(bit, &status, PCI_NUM_INTX + INTX_SHIFT) { > > - /* Clear the INTx */ > > - writel(1 << bit, port->base + PCIE_INT_STATUS); > > virq = irq_find_mapping(port->irq_domain, > > bit - INTX_SHIFT); > > generic_handle_irq(virq); > > + /* Clear the INTx */ > > + writel(1 << bit, port->base + PCIE_INT_STATUS); > > } > > } > > > > @@ -619,10 +619,10 @@ static irqreturn_t mtk_pcie_intr_handler(int irq, void *data) > > > > while ((imsi_status = readl(port->base + PCIE_IMSI_STATUS))) { > > for_each_set_bit(bit, &imsi_status, MTK_MSI_IRQS_NUM) { > > - /* Clear the MSI */ > > - writel(1 << bit, port->base + PCIE_IMSI_STATUS); > > virq = irq_find_mapping(port->msi_domain, bit); > > generic_handle_irq(virq); > > + /* Clear the MSI */ > > + writel(1 << bit, port->base + PCIE_IMSI_STATUS); > > } > > } > > /* Clear MSI interrupt status */ > > -- > > 2.6.4 > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel