pciehp: fix slow probing

Fix the "pciehp probing slow" problem reported from Jan C. Nordholz in
http://bugzilla.kernel.org/show_bug.cgi?id=10751.

The command completed bit in Slot Status register applies only to
commands issued to control the attention indicator, power indicator,
power controller, or electromechanical interlock. However, writes to
other parts of the Slot Control register would end up writing to the
control fields. Hence, any write to Slot Control register is
considered as a command. However, if the controller doesn't support
any of attention indicator, power indicator, power controller and
electromechanical interlock, command completed bit would not set in
writing to Slot Control register. In this case, we should not wait for
command completed bit set, otherwise all commands would be considered
not completed in timeout seconds (1 sec.).

The cause of the problem is pciehp driver didn't take this situation
into account. This patch changes pciehp to take it into account. This
patch also add the check for "No Command Completed Support" bit in
Slot Capability register. If it is set, we should not wait for command
completed bit set as well.

This problem seems to be revealed by the commit
c27fb883 that fixed the bug that
pciehp did not wait for command completed properly (pciehp just
ignored the command completion event).
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/hotplug/pciehp.h

@@ -97,6 +97,7 @@ struct controller {
 	u8 cap_base;
 	struct timer_list poll_timer;
 	volatile int cmd_busy;
+	unsigned int no_cmd_complete:1;
 };
 
 #define INT_BUTTON_IGNORE		0
@@ -135,6 +136,7 @@ struct controller {
 #define PWR_LED_PRSN	0x00000010
 #define HP_SUPR_RM_SUP	0x00000020
 #define EMI_PRSN	0x00020000
+#define NO_CMD_CMPL_SUP	0x00040000
 
 #define ATTN_BUTTN(ctrl)	((ctrl)->slot_cap & ATTN_BUTTN_PRSN)
 #define POWER_CTRL(ctrl)	((ctrl)->slot_cap & PWR_CTRL_PRSN)
@@ -143,6 +145,7 @@ struct controller {
 #define PWR_LED(ctrl)		((ctrl)->slot_cap & PWR_LED_PRSN)
 #define HP_SUPR_RM(ctrl)	((ctrl)->slot_cap & HP_SUPR_RM_SUP)
 #define EMI(ctrl)		((ctrl)->slot_cap & EMI_PRSN)
+#define NO_CMD_CMPL(ctrl)	((ctrl)->slot_cap & NO_CMD_CMPL_SUP)
 
 extern int pciehp_sysfs_enable_slot(struct slot *slot);
 extern int pciehp_sysfs_disable_slot(struct slot *slot);

drivers/pci/hotplug/pciehp_hpc.c

@@ -286,12 +286,28 @@ static int pcie_write_cmd(struct controller *ctrl, u16 cmd, u16 mask)
 		goto out;
 	}
 
-	if ((slot_status & CMD_COMPLETED) == CMD_COMPLETED ) {
-		/* After 1 sec and CMD_COMPLETED still not set, just
-		   proceed forward to issue the next command according
-		   to spec.  Just print out the error message */
+	if (slot_status & CMD_COMPLETED) {
+		if (!ctrl->no_cmd_complete) {
+			/*
+			 * After 1 sec and CMD_COMPLETED still not set, just
+			 * proceed forward to issue the next command according
+			 * to spec. Just print out the error message.
+			 */
 			dbg("%s: CMD_COMPLETED not clear after 1 sec.\n",
 			    __func__);
+		} else if (!NO_CMD_CMPL(ctrl)) {
+			/*
+			 * This controller semms to notify of command completed
+			 * event even though it supports none of power
+			 * controller, attention led, power led and EMI.
+			 */
+			dbg("%s: Unexpected CMD_COMPLETED. Need to wait for "
+			    "command completed event.\n", __func__);
+			ctrl->no_cmd_complete = 0;
+		} else {
+			dbg("%s: Unexpected CMD_COMPLETED. Maybe the "
+			    "controller is broken.\n", __func__);
+		}
 	}
 
 	retval = pciehp_readw(ctrl, SLOTCTRL, &slot_ctrl);
@@ -315,7 +331,7 @@ static int pcie_write_cmd(struct controller *ctrl, u16 cmd, u16 mask)
 	/*
 	 * Wait for command completion.
 	 */
-	if (!retval)
+	if (!retval && !ctrl->no_cmd_complete)
 		retval = pcie_wait_cmd(ctrl);
  out:
 	mutex_unlock(&ctrl->ctrl_lock);
@@ -1130,6 +1146,7 @@ static inline void dbg_ctrl(struct controller *ctrl)
 	dbg("  Power Indicator      : %3s\n", PWR_LED(ctrl)    ? "yes" : "no");
 	dbg("  Hot-Plug Surprise    : %3s\n", HP_SUPR_RM(ctrl) ? "yes" : "no");
 	dbg("  EMI Present          : %3s\n", EMI(ctrl)        ? "yes" : "no");
+	dbg("  Comamnd Completed    : %3s\n", NO_CMD_CMPL(ctrl)? "no" : "yes");
 	pciehp_readw(ctrl, SLOTSTATUS, &reg16);
 	dbg("Slot Status            : 0x%04x\n", reg16);
 	pciehp_readw(ctrl, SLOTSTATUS, &reg16);
@@ -1161,6 +1178,15 @@ int pcie_init(struct controller *ctrl, struct pcie_device *dev)
 	mutex_init(&ctrl->ctrl_lock);
 	init_waitqueue_head(&ctrl->queue);
 	dbg_ctrl(ctrl);
+	/*
+	 * Controller doesn't notify of command completion if the "No
+	 * Command Completed Support" bit is set in Slot Capability
+	 * register or the controller supports none of power
+	 * controller, attention led, power led and EMI.
+	 */
+	if (NO_CMD_CMPL(ctrl) ||
+	    !(POWER_CTRL(ctrl) | ATTN_LED(ctrl) | PWR_LED(ctrl) | EMI(ctrl)))
+	    ctrl->no_cmd_complete = 1;
 
 	info("HPC vendor_id %x device_id %x ss_vid %x ss_did %x\n",
 	     pdev->vendor, pdev->device,