PCI: pciehp: Add quirk for Command Completed errata

Several PCIe hotplug controllers have errata that mean they do 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 Intel erratum CF118.  We assume this applies to all
Intel parts:

  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.

Per Sinan, the Qualcomm QDF2400 controller also does not set the Command
Completed bit unless writes to the Slot Command register change "Control"
bits.

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>	# Lenovo X60
Tested-by: Paul Menzel <pmenzel+linux-pci@molgen.mpg.de>	# Lenovo X60
Signed-off-by: Sinan Kaya <okaya@codeaurora.org>		# Qcom quirk
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 39 insertions, 12 deletions

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 18a42f8f5dc5..74a7f7bde263 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;
@@ -189,6 +186,17 @@ static void pcie_do_write_cmd(struct controller *ctrl, u16 cmd,
 	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 +900,21 @@ 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);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_QCOM, 0x0400,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);
+DECLARE_PCI_FIXUP_CLASS_EARLY(PCI_VENDOR_ID_QCOM, 0x0401,
+			      PCI_CLASS_BRIDGE_PCI, 8, quirk_cmd_compl);