i40e: Error handling for link event

There exists an intermittent bug which causes the 'Link Detected'
field reported by the 'ethtool <iface>' command to be 'Yes' when
in fact, there is no link. This patch fixes the problem by
enabling temporary link polling when i40e_get_link_status returns
an error. This causes the driver to remember that an admin queue
command failed and polls, until the function returns with a success.

Change-Id: I64c69b008db4017b8729f3fc27b8f65c8fe2eaa0
Signed-off-by: Harshitha Ramamurthy <[e-mail]>
Tested-by: Andrew Bowers <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>

drivers/net/ethernet/intel/i40e/i40e.h

···
 #define I40E_FLAG_HAVE_CRT_RETIMER		BIT_ULL(52)
 #define I40E_FLAG_PTP_L4_CAPABLE		BIT_ULL(53)
 #define I40E_FLAG_WOL_MC_MAGIC_PKT_WAKE		BIT_ULL(54)
+#define I40E_FLAG_TEMP_LINK_POLLING		BIT_ULL(55)
 
 	/* tracks features that get auto disabled by errors */
 	u64 auto_disable_flags;

drivers/net/ethernet/intel/i40e/i40e_main.c

···
 	old_link = (pf->hw.phy.link_info_old.link_info & I40E_AQ_LINK_UP);
 
 	status = i40e_get_link_status(&pf->hw, &new_link);
-	if (status) {
+
+	/* On success, disable temp link polling */
+	if (status == I40E_SUCCESS) {
+		if (pf->flags & I40E_FLAG_TEMP_LINK_POLLING)
+			pf->flags &= ~I40E_FLAG_TEMP_LINK_POLLING;
+	} else {
+		/* Enable link polling temporarily until i40e_get_link_status
+		 * returns I40E_SUCCESS
+		 */
+		pf->flags |= I40E_FLAG_TEMP_LINK_POLLING;
 		dev_dbg(&pf->pdev->dev, "couldn't get link state, status: %d\n",
 			status);
 		return;
···
 		return;
 	pf->service_timer_previous = jiffies;
 
-	if (pf->flags & I40E_FLAG_LINK_POLLING_ENABLED)
+	if ((pf->flags & I40E_FLAG_LINK_POLLING_ENABLED) ||
+	    (pf->flags & I40E_FLAG_TEMP_LINK_POLLING))
 		i40e_link_event(pf);
 
 	/* Update the stats for active netdevs so the network stack