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Date:   Fri, 4 May 2018 08:33:27 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     okaya@codeaurora.org
Cc:     Paul Menzel <pmenzel+linux-pci@molgen.mpg.de>,
        Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, Lukas Wunner <lukas@wunner.de>
Subject: Re: pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038
 (issued 65284 msec ago)
Message-ID: <20180504133327.GF15790@bhelgaas-glaptop.roam.corp.google.com>
References: <8770820b-85a0-172b-7230-3a44524e6c9f@molgen.mpg.de>
 <20180427192207.GG8199@bhelgaas-glaptop.roam.corp.google.com>
 <43b8ab4a-f8ee-dc96-40ec-e6fdfedd8309@molgen.mpg.de>
 <20180504024527.GE15790@bhelgaas-glaptop.roam.corp.google.com>
 <aa72d3ba089c76449600c22b58a2cafe@codeaurora.org>
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On Fri, May 04, 2018 at 07:37:40AM +0100, okaya@codeaurora.org wrote:
> On 2018-05-04 03:45, Bjorn Helgaas wrote:
> > On Thu, May 03, 2018 at 10:49:24AM +0200, Paul Menzel wrote:
> > > On 04/27/18 21:22, Bjorn Helgaas wrote:
> > > > [+cc Lukas, Sinan]
> > > 
> > > > On Thu, Apr 26, 2018 at 12:17:53PM +0200, Paul Menzel wrote:
> > > 
> > > > > On the Lenovo X60t, during resume from ACPI suspend and during shutdown, the
> > > > > message below is shown in the logs.
> > > > >
> > > > >      pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued
> > > > > 65284 msec ago)
> > > >
> > > > This is an Intel root port:
> > > >
> > > >    00:1c.0 PCI bridge: Intel Corporation NM10/ICH7 Family PCI Express Port 1 (rev 02) (prog-if 00 [Normal decode])
> > > >
> > > > and probably has the CF118 erratum (see
> > > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3461a068661c
> > > > for details).  I bet if you changed "msecs" in pcie_wait_cmd() to 30000
> > > > you'd see a 30 second delay during shutdown because we write a command to
> > > > tell the port not to generate any more hotplug interrupts, and we wait for
> > > > that command to complete, but the port never tells us it has completed.
> > > >
> > > > Lukas reported a similar issue in
> > > > https://lkml.kernel.org/r/20180112104929.GA10599@wunner.de, which we sort
> > > > of worked around by assuming that Thunderbolt controllers never support
> > > > that "command complete" interrupt (see
> > > > http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=493fb50e958c)
> > > >
> > > > Sinan mooted the idea of using a "no-wait" path of sending the "don't
> > > > generate hotplug interrupts" command.  I think we should work on this
> > > > idea a little more.  If we're shutting down the whole system, I can't
> > > > believe there's much value in *anything* we do in the pciehp_remove()
> > > > path.
> > > >
> > > > Maybe we should just get rid of pciehp_remove() (and probably
> > > > pcie_port_remove_service() and the other service driver remove methods)
> > > > completely.  That dates from when the service drivers could be modules that
> > > > could be potentially unloaded, but unloading them hasn't been possible for
> > > > years.
> > > >
> > > > As far as the resume path, my guess is that in pciehp_resume(), we
> > > > write a command to enable interrupts, then it looks like we get a
> > > > PCI_EXP_SLTSTA_DLLSC "Link Up" interrupt, and apparently we issue
> > > > another command.  Not sure exactly what's going on here.
> > 
> > > Thank you for the quick reply and sorry for only being able to test
> > > it now.
> > > Please find the relevant bits from the ACPI S3 suspend “action”
> > > below. The
> > > full log is attached.
> > 
> > No problem.  I think we need to bite the bullet and just do a quirk
> > for the Intel erratum.  I tried to avoid it by waiting for command
> > completion lazily, but I think that ended up being unnecessarily
> > clever and it didn't even solve the whole problem.
> > 
> > Can you try the patch below?  I think it should solve the problem
> > you're seeing.
> > ...

> > +	/* Assume all Intel controllers have erratum CF118 */
> > +	if (pdev->vendor == PCI_VENDOR_ID_INTEL)
> > +		ctrl->cc_erratum = 1;
> > +
> 
> Can we build a table like quirks.c?
> 
> Qdf2400 root ports have the same problem. I will do a follow up patch once
> this finds its way in.

Yes, definitely.  I intended to do that but got a little lazy.  What
do you think about the following?  Paul, if you haven't tested the
first patch, can you try this one instead?  The logic is pretty much
the same.

3461a068661c ("PCI: pciehp: Wait for hotplug command completion
lazily") mentions AMD and Nvidia devices with the same issue, but
unfortunately doesn't include any specifics.


commit b0d6f2230e12c85ae3b65a854a53c67c7c1f6406
Author: Bjorn Helgaas <bhelgaas@google.com>
Date:   Thu May 3 18:39:38 2018 -0500

    PCI: pciehp: Add quirk for Intel Command Completed erratum
    
    The Intel CF118 erratum means the controller does not set the Command
    Completed bit unless writes to the Slot Command register change "Control"
    bits.  Command Completed is never set for writes that only change software
    notification "Enable" bits.  This results in timeouts like this:
    
      pciehp 0000:00:1c.0:pcie004: Timeout on hotplug command 0x1038 (issued 65284 msec ago)
    
    When this erratum is present, avoid these timeouts by marking commands
    "completed" immediately unless they change the "Control" bits.
    
    Here's the text of the erratum from the Intel document:
    
      CF118        PCIe Slot Status Register Command Completed bit not always
                   updated on any configuration write to the Slot Control
                   Register
    
      Problem:     For PCIe root ports (devices 0 - 10) supporting hot-plug,
                   the Slot Status Register (offset AAh) Command Completed
                   (bit[4]) status is updated under the following condition:
                   IOH will set Command Completed bit after delivering the new
                   commands written in the Slot Controller register (offset
                   A8h) to VPP. The IOH detects new commands written in Slot
                   Control register by checking the change of value for Power
                   Controller Control (bit[10]), Power Indicator Control
                   (bits[9:8]), Attention Indicator Control (bits[7:6]), or
                   Electromechanical Interlock Control (bit[11]) fields. Any
                   other configuration writes to the Slot Control register
                   without changing the values of these fields will not cause
                   Command Completed bit to be set.
    
                   The PCIe Base Specification Revision 2.0 or later describes
                   the “Slot Control Register” in section 7.8.10, as follows
                   (Reference section 7.8.10, Slot Control Register, Offset
                   18h). In hot-plug capable Downstream Ports, a write to the
                   Slot Control register must cause a hot-plug command to be
                   generated (see Section 6.7.3.2 for details on hot-plug
                   commands). A write to the Slot Control register in a
                   Downstream Port that is not hotplug capable must not cause a
                   hot-plug command to be executed.
    
                   The PCIe Spec intended that every write to the Slot Control
                   Register is a command and expected a command complete status
                   to abstract the VPP implementation specific nuances from the
                   OS software. IOH PCIe Slot Control Register implementation
                   is not fully conforming to the PCIe Specification in this
                   respect.
    
      Implication: Software checking on the Command Completed status after
                   writing to the Slot Control register may time out.
    
      Workaround:  Software can read the Slot Control register and compare the
                   existing and new values to determine if it should check the
                   Command Completed status after writing to the Slot Control
                   register.
    
    Link: http://www.intel.com/content/www/us/en/processors/xeon/xeon-e7-v2-spec-update.html
    Link: https://lkml.kernel.org/r/8770820b-85a0-172b-7230-3a44524e6c9f@molgen.mpg.de
    Reported-by: Paul Menzel <pmenzel+linux-pci@molgen.mpg.de>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 18a42f8f5dc5..e70eba5ea906 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -10,7 +10,6 @@
  * All rights reserved.
  *
  * Send feedback to <greg@kroah.com>,<kristen.c.accardi@intel.com>
- *
  */
 
 #include <linux/kernel.h>
@@ -147,25 +146,22 @@ static void pcie_wait_cmd(struct controller *ctrl)
 	else
 		rc = pcie_poll_cmd(ctrl, jiffies_to_msecs(timeout));
 
-	/*
-	 * Controllers with errata like Intel CF118 don't generate
-	 * completion notifications unless the power/indicator/interlock
-	 * control bits are changed.  On such controllers, we'll emit this
-	 * timeout message when we wait for completion of commands that
-	 * don't change those bits, e.g., commands that merely enable
-	 * interrupts.
-	 */
 	if (!rc)
 		ctrl_info(ctrl, "Timeout on hotplug command %#06x (issued %u msec ago)\n",
 			  ctrl->slot_ctrl,
 			  jiffies_to_msecs(jiffies - ctrl->cmd_started));
 }
 
+#define CC_ERRATUM_MASK		(PCI_EXP_SLTCTL_PCC |	\
+				 PCI_EXP_SLTCTL_PIC |	\
+				 PCI_EXP_SLTCTL_AIC |	\
+				 PCI_EXP_SLTCTL_EIC)
+
 static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 			      u16 mask, bool wait)
 {
 	struct pci_dev *pdev = ctrl_dev(ctrl);
-	u16 slot_ctrl;
+	u16 slot_ctrl_orig, slot_ctrl;
 
 	mutex_lock(&ctrl->ctrl_lock);
 
@@ -180,6 +176,7 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 		goto out;
 	}
 
+	slot_ctrl_orig = slot_ctrl;
 	slot_ctrl &= ~mask;
 	slot_ctrl |= (cmd & mask);
 	ctrl->cmd_busy = 1;
@@ -188,6 +185,17 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 	ctrl->cmd_started = jiffies;
 	ctrl->slot_ctrl = slot_ctrl;
 
+	/*
+	 * Controllers with the Intel CF118 and similar errata advertise
+	 * Command Completed support, but they only set Command Completed
+	 * if we change the "Control" bits for power, power indicator,
+	 * attention indicator, or interlock.  If we only change the
+	 * "Enable" bits, they never set the Command Completed bit.
+	 */
+	if (pdev->broken_cmd_compl &&
+	    (slot_ctrl_orig & CC_ERRATUM_MASK) == (slot_ctrl & CC_ERRATUM_MASK))
+		ctrl->cmd_busy = 0;
+
 	/*
 	 * Optionally wait for the hardware to be ready for a new command,
 	 * indicating completion of the above issued command.
@@ -861,7 +869,7 @@ struct controller *pcie_init(struct pcie_device *dev)
 		PCI_EXP_SLTSTA_MRLSC | PCI_EXP_SLTSTA_CC |
 		PCI_EXP_SLTSTA_DLLSC);
 
-	ctrl_info(ctrl, "Slot #%d AttnBtn%c PwrCtrl%c MRL%c AttnInd%c PwrInd%c HotPlug%c Surprise%c Interlock%c NoCompl%c LLActRep%c\n",
+	ctrl_info(ctrl, "Slot #%d AttnBtn%c PwrCtrl%c MRL%c AttnInd%c PwrInd%c HotPlug%c Surprise%c Interlock%c NoCompl%c LLActRep%c%s\n",
 		(slot_cap & PCI_EXP_SLTCAP_PSN) >> 19,
 		FLAG(slot_cap, PCI_EXP_SLTCAP_ABP),
 		FLAG(slot_cap, PCI_EXP_SLTCAP_PCP),
@@ -872,7 +880,8 @@ struct controller *pcie_init(struct pcie_device *dev)
 		FLAG(slot_cap, PCI_EXP_SLTCAP_HPS),
 		FLAG(slot_cap, PCI_EXP_SLTCAP_EIP),
 		FLAG(slot_cap, PCI_EXP_SLTCAP_NCCS),
-		FLAG(link_cap, PCI_EXP_LNKCAP_DLLLARC));
+		FLAG(link_cap, PCI_EXP_LNKCAP_DLLLARC),
+		pdev->broken_cmd_compl ? " (with Cmd Compl erratum)" : "");
 
 	if (pcie_init_slot(ctrl))
 		goto abort_ctrl;
@@ -891,3 +900,17 @@ void pciehp_release_ctrl(struct controller *ctrl)
 	pcie_cleanup_slot(ctrl);
 	kfree(ctrl);
 }
+
+static void quirk_cmd_compl(struct pci_dev *pdev)
+{
+	u32 slot_cap;
+
+	if (pci_is_pcie(pdev)) {
+		pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, &slot_cap);
+		if (slot_cap & PCI_EXP_SLTCAP_HPC &&
+		    !(slot_cap & PCI_EXP_SLTCAP_NCCS))
+			pdev->broken_cmd_compl = 1;
+	}
+}
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_INTEL, PCI_ANY_ID,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 73178a2fcee0..60cb5350ad28 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -406,6 +406,9 @@ struct pci_dev {
 	struct bin_attribute *res_attr[DEVICE_COUNT_RESOURCE]; /* sysfs file for resources */
 	struct bin_attribute *res_attr_wc[DEVICE_COUNT_RESOURCE]; /* sysfs file for WC mapping of resources */
 
+#ifdef CONFIG_HOTPLUG_PCI_PCIE
+	unsigned int	broken_cmd_compl:1;	/* Command Complete broken */
+#endif
 #ifdef CONFIG_PCIE_PTM
 	unsigned int	ptm_root:1;
 	unsigned int	ptm_enabled:1;