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

Benjamin Poirier
2017-12-08T08:34:48Z

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.ï¿½ï¿½If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Benjamin Poirier <bpoirier@suse.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
> > ï¿½ *ï¿½ï¿½Checks to see of the link status of the hardware has changed.ï¿½ï¿½If a
> > ï¿½ *ï¿½ï¿½change in link status has been detected, then we read the PHY registers
> > ï¿½ *ï¿½ï¿½to get the current speed/duplex if link exists.
> > + *
> > + *ï¿½ï¿½Returns a negative error code (-E1000_ERR_*) or 0 (link down) or 1 (link
> > + *ï¿½ï¿½up).
> > ï¿½ **/
> > ï¿½s32 e1000e_check_for_copper_link(struct e1000_hw *hw)
> > ï¿½{
> [...]
> > --- 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
> > > ï¿½ case e1000_media_type_copper:
> > > ï¿½ if (hw->mac.get_link_status) {
> > > ï¿½ ret_val = hw->mac.ops.check_for_link(hw);
> > > - link_active = !hw->mac.get_link_status;
> > > + link_active = ret_val > 0;
> > > ï¿½ } else {
> > > ï¿½ link_active = true;
> > > ï¿½ }
>
> 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