From patchwork Wed Aug 23 22:24:36 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bjorn Helgaas X-Patchwork-Id: 9918539 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8C977602CB for ; Wed, 23 Aug 2017 22:24:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7EB2828A99 for ; Wed, 23 Aug 2017 22:24:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 739D528A9E; Wed, 23 Aug 2017 22:24:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1464728AA0 for ; Wed, 23 Aug 2017 22:24:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751003AbdHWWYl (ORCPT ); Wed, 23 Aug 2017 18:24:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:44518 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751143AbdHWWYj (ORCPT ); Wed, 23 Aug 2017 18:24:39 -0400 Received: from localhost (unknown [69.71.4.159]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2371A21A1C; Wed, 23 Aug 2017 22:24:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2371A21A1C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=helgaas@kernel.org Date: Wed, 23 Aug 2017 17:24:36 -0500 From: Bjorn Helgaas To: Sinan Kaya Cc: linux-pci@vger.kernel.org, timur@codeaurora.org, alex.williamson@redhat.com, linux-arm-msm@vger.kernel.org, Bjorn Helgaas , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH V12 4/5] PCI: Handle CRS ("device not ready") returned by device after FLR Message-ID: <20170823222436.GH8498@bhelgaas-glaptop.roam.corp.google.com> References: <1503464171-6471-1-git-send-email-okaya@codeaurora.org> <1503464171-6471-4-git-send-email-okaya@codeaurora.org> <20170823213838.GG8498@bhelgaas-glaptop.roam.corp.google.com> <0ef4c01d-75bc-17dc-8926-2f9647cfeec8@codeaurora.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0ef4c01d-75bc-17dc-8926-2f9647cfeec8@codeaurora.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Wed, Aug 23, 2017 at 05:51:19PM -0400, Sinan Kaya wrote: > On 8/23/2017 5:38 PM, Bjorn Helgaas wrote: > > If we increase the timeout, is there still value in adding the > > pci_bus_wait_crs() stuff? I'm not sure there is. > > I agree increasing the timeout is more than enough for FLR case. If that's the case, I think there's no value in adding additional complexity to the path. If we increase the timeout, we might pretty it up a little along the lines of the patch below. > However, I was considering the wait and pending functions as a utility > that I can reuse towards fixing CRS in other conditions like secondary > bus reset and potentially PM. > > I'm planning to have a CRS session in the Linux Plumbers Conference > to talk about CRS use cases. Great idea. I'm kind of confused on its value in general myself. And there's now a new mechanism (Function Readiness Status) that I don't think we have any support for at all. > I was going to follow up this series with secondary bus reset next once > this goes in. I think I'm OK with everything except the pci_flr_wait() change. The rest of it makes sense (although I don't think there are any users outside probe.c, so maybe should be static for now). > I'm unable to test PM. I can't promise how I fix/test it. --- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index af0cc3456dc1..b04c99e60b77 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -3811,27 +3811,50 @@ int pci_wait_for_pending_transaction(struct pci_dev *dev) } EXPORT_SYMBOL(pci_wait_for_pending_transaction); -/* - * We should only need to wait 100ms after FLR, but some devices take longer. - * Wait for up to 1000ms for config space to return something other than -1. - * Intel IGD requires this when an LCD panel is attached. We read the 2nd - * dword because VFs don't implement the 1st dword. - */ static void pci_flr_wait(struct pci_dev *dev) { - int i = 0; + int delay = 1, timeout = 60000; u32 id; - do { - msleep(100); + /* + * Per PCIe r3.1, sec 6.6.2, a device must complete an FLR within + * 100ms, but may silently discard requests while the FLR is in + * progress. Wait 100ms before trying to access the device. + */ + msleep(100); + + /* + * After 100ms, the device should not silently discard config + * requests, but it may still indicate that it needs more time by + * responding to them with CRS completions. The Root Port will + * generally synthesize ~0 data to complete the read (except when + * CRS SV is enabled and the read was for the Vendor ID; in that + * case it synthesizes 0x0001 data). + * + * Wait for the device to return a non-CRS completion. Read the + * Command register instead of Vendor ID so we don't have to + * contend with the CRS SV value. + */ + pci_read_config_dword(dev, PCI_COMMAND, &id); + while (id == ~0) { + if (delay > timeout) { + dev_warn(&dev->dev, "not ready %dms after FLR; giving up\n", + delay - 1); + return; + } + + if (delay > 1000) + dev_info(&dev->dev, "not ready %dms after FLR; waiting\n", + delay - 1); + + msleep(delay); + delay *= 2; + pci_read_config_dword(dev, PCI_COMMAND, &id); - } while (i++ < 10 && id == ~0); + } - if (id == ~0) - dev_warn(&dev->dev, "Failed to return from FLR\n"); - else if (i > 1) - dev_info(&dev->dev, "Required additional %dms to return from FLR\n", - (i - 1) * 100); + if (delay > 1000) + dev_info(&dev->dev, "ready %dms after FLR\n", delay - 1); } /**