linux-kernel - Re: [PATCH 4.4 71/96] e1000e: Separate signaling for link check/link up

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Date:   Fri, 8 Dec 2017 17:34:41 +0900
From:   Benjamin Poirier <bpoirier@...e.com>
To:     Ben Hutchings <ben.hutchings@...ethink.co.uk>
Cc:     Gabriel C <nix.or.die@...il.com>, Christian Hesse <list@...rm.de>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        stable@...r.kernel.org,
        Lennart Sorensen <lsorense@...lub.uwaterloo.ca>,
        Aaron Brown <aaron.f.brown@...el.com>,
        Amit Pundir <amit.pundir@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.4 71/96] e1000e: Separate signaling for link check/link
 up

On 2017/12/07 20:02, Ben Hutchings wrote:
> On Tue, 2017-11-28 at 11:23 +0100, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Benjamin Poirier <bpoirier@...e.com>
> > 
> > commit 19110cfbb34d4af0cdfe14cd243f3b09dc95b013 upstream.
> [...]
> > --- a/drivers/net/ethernet/intel/e1000e/mac.c
> > +++ b/drivers/net/ethernet/intel/e1000e/mac.c
> > @@ -410,6 +410,9 @@ void e1000e_clear_hw_cntrs_base(struct e
> >   *  Checks to see of the link status of the hardware has changed.  If a
> >   *  change in link status has been detected, then we read the PHY registers
> >   *  to get the current speed/duplex if link exists.
> > + *
> > + *  Returns a negative error code (-E1000_ERR_*) or 0 (link down) or 1 (link
> > + *  up).
> >   **/
> >  s32 e1000e_check_for_copper_link(struct e1000_hw *hw)
> >  {
> [...]
> > --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> > +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> > @@ -5017,7 +5017,7 @@ static bool e1000e_has_link(struct e1000
> > >  	case e1000_media_type_copper:
> > >  		if (hw->mac.get_link_status) {
> > >  			ret_val = hw->mac.ops.check_for_link(hw);
> > > -			link_active = !hw->mac.get_link_status;
> > > +			link_active = ret_val > 0;
> > >  		} else {
> > >  			link_active = true;
> > >  		}
> 
> As this change in e1000e_has_link() is conditional only on the media
> type, doesn't e1000_check_for_copper_link_ich8lan() also need to be
> changed to return 1 for link up?

You're right. I looked at it again, in the commit log I wrote that
"hw->mac.ops.check_for_link(hw) === e1000e_check_for_copper_link" which
is true for the race condition reported (because that's the function in
use on adapters that have msix vectors mac.type == e1000_82574) but not
generally true. The other check_for_link callback needs to be adjusted
likewise.

However, I happen to have a I218-LM (e1000_pch_lpt) so I tested 4.14.3
and this error only delays link up, it doesn't prevent it.
e1000_check_for_copper_link_ich8lan() sets mac->get_link_status = false;
and on the next watchdog execution, we fall in the second branch of the
following e1000e_has_link code:

	case e1000_media_type_copper:
		if (hw->mac.get_link_status) {
			ret_val = hw->mac.ops.check_for_link(hw);
			link_active = ret_val > 0;
		} else {
			link_active = true;

OTOH, there are multiple reports in
https://bugzilla.kernel.org/show_bug.cgi?id=198047
that reverting 830466993daf ("e1000e: Separate signaling for link
check/link up") fixes the issue so there's something I'm missing.

Gabriel and Christian, can you test the following patch?

diff --git a/drivers/net/ethernet/intel/e1000e/ich8lan.c b/drivers/net/ethernet/intel/e1000e/ich8lan.c
index d6d4ed7acf03..31277d3bb7dc 100644
--- a/drivers/net/ethernet/intel/e1000e/ich8lan.c
+++ b/drivers/net/ethernet/intel/e1000e/ich8lan.c
@@ -1367,6 +1367,9 @@ static s32 e1000_disable_ulp_lpt_lp(struct e1000_hw *hw, bool force)
  *  Checks to see of the link status of the hardware has changed.  If a
  *  change in link status has been detected, then we read the PHY registers
  *  to get the current speed/duplex if link exists.
+ *
+ *  Returns a negative error code (-E1000_ERR_*) or 0 (link down) or 1 (link
+ *  up).
  **/
 static s32 e1000_check_for_copper_link_ich8lan(struct e1000_hw *hw)
 {
@@ -1382,7 +1385,7 @@ static s32 e1000_check_for_copper_link_ich8lan(struct e1000_hw *hw)
 	 * Change or Rx Sequence Error interrupt.
 	 */
 	if (!mac->get_link_status)
-		return 0;
+		return 1;
 
 	/* First we want to see if the MII Status Register reports
 	 * link.  If so, then we want to get the current speed/duplex
@@ -1613,10 +1616,12 @@ static s32 e1000_check_for_copper_link_ich8lan(struct e1000_hw *hw)
 	 * different link partner.
 	 */
 	ret_val = e1000e_config_fc_after_link_up(hw);
-	if (ret_val)
+	if (ret_val) {
 		e_dbg("Error configuring flow control\n");
+		return ret_val;
+	}
 
-	return ret_val;
+	return 1;
 }
 
 static s32 e1000_get_variants_ich8lan(struct e1000_adapter *adapter)
-- 
2.15.1