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Date: Mon, 21 Aug 2017 10:02:55 -0400 From: Sinan Kaya <okaya@...eaurora.org> To: Bjorn Helgaas <bhelgaas@...gle.com> 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: Re: [PATCH v11 1/4] PCI: Don't ignore valid response before CRS timeout On 8/18/2017 5:32 PM, Bjorn Helgaas wrote: > 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. */ > + There is still a problem here. We'll wait some time above and return without checking if we actually found the card or not. > 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; > > Here is another shot at it. Sorry, I don't have a diff syntax. I made up the function by copy paste. while ((*l & 0xffff) == 0x0001) { if (!crs_timeout) 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; } msleep(delay); delay *= 2; if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, l)) return false; } -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
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