linux-kernel - [PATCH v11 1/4] PCI: Don't ignore valid response before CRS timeout

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Message-ID: <20170818213203.15145.36487.stgit@bhelgaas-glaptop.roam.corp.google.com>
Date:   Fri, 18 Aug 2017 16:32:03 -0500
From:   Bjorn Helgaas <bhelgaas@...gle.com>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     linux-pci@...r.kernel.org, Timur Tabi <timur@...eaurora.org>,
        linux-kernel@...r.kernel.org,
        Alex Williamson <alex.williamson@...hat.com>,
        linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v11 1/4] PCI: Don't ignore valid response before CRS timeout

While waiting for a device to become ready (i.e., to return a non-CRS
completion to a read of its Vendor ID), if we got a valid response to the
very last read before timing out, we printed a warning and gave up on the
device even though it was actually ready.

For a typical 60s timeout, we wait about 65s (it's not exact because of the
exponential backoff), but we treated devices that became ready between 33s
and 65s as though they failed.

Move the Device ID read later so we check whether the device is ready
immediately, before checking for a timeout.

Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 drivers/pci/probe.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index c31310db0404..08ea844ac4ba 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1849,15 +1849,16 @@ bool pci_bus_read_dev_vendor_id(struct pci_bus *bus, int devfn, u32 *l,
 
 		msleep(delay);
 		delay *= 2;
-		if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, l))
-			return false;
-		/* Card hasn't responded in 60 seconds?  Must be stuck. */
+
 		if (delay > crs_timeout) {
 			printk(KERN_WARNING "pci %04x:%02x:%02x.%d: not responding\n",
 			       pci_domain_nr(bus), bus->number, PCI_SLOT(devfn),
 			       PCI_FUNC(devfn));
 			return false;
 		}
+
+		if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, l))
+			return false;
 	}
 
 	return true;