PCI hotplug: pciehp: poll data link layer link active

This patch adds polling mechanism for Data Link Layer Link Active bit
after turning power on, instead of waiting for 1000 msec. This reduces
reduce the unnecessary long wait.
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/hotplug/pciehp.h

@@ -110,6 +110,7 @@ struct controller {
 	struct timer_list poll_timer;
 	int cmd_busy;
 	unsigned int no_cmd_complete:1;
+	unsigned int link_active_reporting:1;
 };
 
 #define INT_BUTTON_IGNORE		0

drivers/pci/hotplug/pciehp_ctrl.c

@@ -226,9 +226,6 @@ static int board_added(struct slot *p_slot)
 	if (PWR_LED(ctrl))
 		p_slot->hpc_ops->green_led_blink(p_slot);
 
-	/* Wait for ~1 second */
-	msleep(1000);
-
 	/* Check link training status */
 	retval = p_slot->hpc_ops->check_lnk_status(ctrl);
 	if (retval) {

drivers/pci/hotplug/pciehp_hpc.c

@@ -125,6 +125,7 @@ static inline int pciehp_writel(struct controller *ctrl, int reg, u32 value)
 /* Field definitions in Link Capabilities Register */
 #define MAX_LNK_SPEED		0x000F
 #define MAX_LNK_WIDTH		0x03F0
+#define LINK_ACTIVE_REPORTING	0x00100000
 
 /* Link Width Encoding */
 #define LNK_X1		0x01
@@ -141,6 +142,7 @@ static inline int pciehp_writel(struct controller *ctrl, int reg, u32 value)
 #define LNK_TRN_ERR	0x0400
 #define	LNK_TRN		0x0800
 #define SLOT_CLK_CONF	0x1000
+#define LINK_ACTIVE	0x2000
 
 /* Field definitions in Slot Capabilities Register */
 #define ATTN_BUTTN_PRSN	0x00000001
@@ -368,11 +370,52 @@ static int pcie_write_cmd(struct controller *ctrl, u16 cmd, u16 mask)
 	return retval;
 }
 
+static inline int check_link_active(struct controller *ctrl)
+{
+	u16 link_status;
+
+	if (pciehp_readw(ctrl, LNKSTATUS, &link_status))
+		return 0;
+	return !!(link_status & LINK_ACTIVE);
+}
+
+static void pcie_wait_link_active(struct controller *ctrl)
+{
+	int timeout = 1000;
+
+	if (check_link_active(ctrl))
+		return;
+	while (timeout > 0) {
+		msleep(10);
+		timeout -= 10;
+		if (check_link_active(ctrl))
+			return;
+	}
+	ctrl_dbg(ctrl, "Data Link Layer Link Active not set in 1000 msec\n");
+}
+
 static int hpc_check_lnk_status(struct controller *ctrl)
 {
 	u16 lnk_status;
 	int retval = 0;
 
+        /*
+         * Data Link Layer Link Active Reporting must be capable for
+         * hot-plug capable downstream port. But old controller might
+         * not implement it. In this case, we wait for 1000 ms.
+         */
+        if (ctrl->link_active_reporting){
+                /* Wait for Data Link Layer Link Active bit to be set */
+                pcie_wait_link_active(ctrl);
+                /*
+                 * We must wait for 100 ms after the Data Link Layer
+                 * Link Active bit reads 1b before initiating a
+                 * configuration access to the hot added device.
+                 */
+                msleep(100);
+        } else
+                msleep(1000);
+
 	retval = pciehp_readw(ctrl, LNKSTATUS, &lnk_status);
 	if (retval) {
 		ctrl_err(ctrl, "%s: Cannot read LNKSTATUS register\n",
@@ -1131,7 +1174,7 @@ static inline void dbg_ctrl(struct controller *ctrl)
 struct controller *pcie_init(struct pcie_device *dev)
 {
 	struct controller *ctrl;
-	u32 slot_cap;
+	u32 slot_cap, link_cap;
 	struct pci_dev *pdev = dev->port;
 
 	ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
@@ -1173,6 +1216,16 @@ struct controller *pcie_init(struct pcie_device *dev)
 	    !(POWER_CTRL(ctrl) | ATTN_LED(ctrl) | PWR_LED(ctrl) | EMI(ctrl)))
 	    ctrl->no_cmd_complete = 1;
 
+        /* Check if Data Link Layer Link Active Reporting is implemented */
+        if (pciehp_readl(ctrl, LNKCAP, &link_cap)) {
+                ctrl_err(ctrl, "%s: Cannot read LNKCAP register\n", __func__);
+                goto abort_ctrl;
+        }
+        if (link_cap & LINK_ACTIVE_REPORTING) {
+                ctrl_dbg(ctrl, "Link Active Reporting supported\n");
+                ctrl->link_active_reporting = 1;
+        }
+
 	/* Clear all remaining event bits in Slot Status register */
 	if (pciehp_writew(ctrl, SLOTSTATUS, 0x1f))
 		goto abort_ctrl;