PCI: pciehp: Compute timeout from hotplug command start time

If we issue a hotplug command, go do something else, then come back and
wait for the command to complete, we don't have to wait the whole timeout
period, because some of it elapsed while we were doing something else.

Keep track of the time we issued the command, and wait only until the
timeout period from that point has elapsed.

For controllers with errata like Intel CF118, we previously timed out
before issuing the second hotplug command:

  At time T1 (during boot):
    - Write DLLSCE, ABPE, PDCE, etc. to Slot Control
  At time T2 (hotplug event):
    - Wait for command completion (CC) in Slot Status
    - Timeout at T2 + 1 second because CC is never set in Slot Status
    - Write PCC, PIC, etc. to Slot Control

With this change, we wait until T1 + 1 second instead of T2 + 1 second.
If the hotplug event is more than 1 second after the boot-time
initialization, we won't wait for the timeout at all.

We still emit a "Timeout on hotplug command" message if it timed out; we
should see this on the first hotplug event on every controller with this
erratum, as well as on real errors on controllers without the erratum.

Link: http://www.intel.com/content/www/us/en/processors/xeon/xeon-e7-v2-spec-update.html
Tested-by: Rajat Jain <rajatxjain@gmail.com>	(IDT 807a controller)
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>

1 files changed, 28 insertions, 5 deletions

diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index b3e700d..720dfe5 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -104,11 +104,10 @@ static inline void pciehp_free_irq(struct controller *ctrl)
 		free_irq(ctrl->pcie->irq, ctrl);
 }
 
-static int pcie_poll_cmd(struct controller *ctrl)
+static int pcie_poll_cmd(struct controller *ctrl, int timeout)
 {
 	struct pci_dev *pdev = ctrl_dev(ctrl);
 	u16 slot_status;
-	int timeout = 1000;
 
 	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &slot_status);
 	if (slot_status & PCI_EXP_SLTSTA_CC) {
@@ -132,7 +131,9 @@ static int pcie_poll_cmd(struct controller *ctrl)
 static void pcie_wait_cmd(struct controller *ctrl)
 {
 	unsigned int msecs = pciehp_poll_mode ? 2500 : 1000;
-	unsigned long timeout = msecs_to_jiffies(msecs);
+	unsigned long duration = msecs_to_jiffies(msecs);
+	unsigned long cmd_timeout = ctrl->cmd_started + duration;
+	unsigned long now, timeout;
 	int rc;
 
 	/*
@@ -145,13 +146,34 @@ static void pcie_wait_cmd(struct controller *ctrl)
 	if (!ctrl->cmd_busy)
 		return;
 
+	/*
+	 * Even if the command has already timed out, we want to call
+	 * pcie_poll_cmd() so it can clear PCI_EXP_SLTSTA_CC.
+	 */
+	now = jiffies;
+	if (time_before_eq(cmd_timeout, now))
+		timeout = 1;
+	else
+		timeout = cmd_timeout - now;
+
 	if (ctrl->slot_ctrl & PCI_EXP_SLTCTL_HPIE &&
 	    ctrl->slot_ctrl & PCI_EXP_SLTCTL_CCIE)
 		rc = wait_event_timeout(ctrl->queue, !ctrl->cmd_busy, timeout);
 	else
-		rc = pcie_poll_cmd(ctrl);
+		rc = pcie_poll_cmd(ctrl, 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_dbg(ctrl, "Command not completed in 1000 msec\n");
+		ctrl_info(ctrl, "Timeout on hotplug command %#010x (issued %u msec ago)\n",
+			  ctrl->slot_ctrl,
+			  jiffies_to_msecs(now - ctrl->cmd_started));
 }
 
 /**
@@ -201,6 +223,7 @@ static void pcie_write_cmd(struct controller *ctrl, u16 cmd, u16 mask)
 	ctrl->cmd_busy = 1;
 	smp_mb();
 	pcie_capability_write_word(pdev, PCI_EXP_SLTCTL, slot_ctrl);
+	ctrl->cmd_started = jiffies;
 	ctrl->slot_ctrl = slot_ctrl;
 
 	mutex_unlock(&ctrl->ctrl_lock);