netdev - [PATCH net-next v2 3/4] net-e1000e: reworked carrier detection logic

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Date:	Tue, 22 Nov 2011 11:23:37 -0800
From:	David Decotigny <david.decotigny@...gle.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	Alex Duyck <alexander.h.duyck@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	David Decotigny <david.decotigny@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ian Campbell <ian.campbell@...rix.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Maciej Żenczykowski <zenczykowski@...il.com>
Subject: [PATCH net-next v2 3/4] net-e1000e: reworked carrier detection logic

From: Maciej Żenczykowski <zenczykowski@...il.com>

This change removes an un-needed final pause in case of timeout and
reworks the "link is up" detection logic.



Signed-off-by: David Decotigny <david.decotigny@...gle.com>
---
 drivers/net/ethernet/intel/e1000e/phy.c |   64 +++++++++++++++++++------------
 1 files changed, 39 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/phy.c b/drivers/net/ethernet/intel/e1000e/phy.c
index 8666476..f487a7f 100644
--- a/drivers/net/ethernet/intel/e1000e/phy.c
+++ b/drivers/net/ethernet/intel/e1000e/phy.c
@@ -1775,39 +1775,53 @@ static s32 e1000_wait_autoneg(struct e1000_hw *hw)
  *  Polls the PHY status register for link, 'iterations' number of times.
  **/
 s32 e1000e_phy_has_link_generic(struct e1000_hw *hw, u32 iterations,
-			       u32 usec_interval, bool *success)
+				u32 usec_interval, bool *success)
 {
-	s32 ret_val = 0;
-	u16 i, phy_status;
+	u32 i;
+	u16 phy_reg;
+	int good_reads_phy_status = 0;
+
+	}
+
+	/*
+	 * Remember that e1e_rphy may fail because of another entity
+	 * (like the firmware) holding the lock, we need to handle
+	 * this gracefully - by waiting and trying again.
+	 *
+	 * Some PHYs require the PHY_STATUS register to be read twice
+	 * due to the link bit being sticky.  No harm doing it across
+	 * the board.
+	 */
+	for (i = 0; i < iterations; /* i incremented manually */) {
+		if (0 == e1e_rphy(hw, PHY_STATUS, &phy_reg)) {
+			if (++good_reads_phy_status < 2)
+				continue; /* Re-read once, to make sure */
 
-	for (i = 0; i < iterations; i++) {
-		/*
-		 * Some PHYs require the PHY_STATUS register to be read
-		 * twice due to the link bit being sticky.  No harm doing
-		 * it across the board.
-		 */
-		ret_val = e1e_rphy(hw, PHY_STATUS, &phy_status);
-		if (ret_val)
 			/*
-			 * If the first read fails, another entity may have
-			 * ownership of the resources, wait and try again to
-			 * see if they have relinquished the resources yet.
+			 * Great, we got at least 2 successfull reads
 			 */
-			udelay(usec_interval);
-		ret_val = e1e_rphy(hw, PHY_STATUS, &phy_status);
-		if (ret_val)
-			break;
-		if (phy_status & MII_SR_LINK_STATUS)
-			break;
-		if (usec_interval >= 1000)
-			mdelay(usec_interval/1000);
+
+			if (phy_reg & MII_SR_LINK_STATUS) {
+				/* success: link up */
+				*success = true;
+				return 0;
+			}
+		}
+
+		/* Pause now and re-iterate */
+		if (++i >= iterations)
+			break; /* Pause not needed after last iteration */
+		else if (usec_interval >= 1000)
+			mdelay(usec_interval / 1000);
 		else
 			udelay(usec_interval);
 	}
 
-	*success = (i < iterations);
-
-	return ret_val;
+	/* no success in for(;;) loop */
+	*success = false;
+	if (good_reads_phy_status < 2)
+		return -E1000_ERR_PHY;
+	return 0;
 }
 
 /**
-- 
1.7.3.1

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