[Intel-wired-lan] [PATCH] e1000e: Ignore TSYNCRXCTL when getting I219 clock attributes

[Brown, Aaron F]

> From: Intel-wired-lan [mailto:intel-wired-lan-bounces at osuosl.org] On
> Behalf Of Benjamin Poirier
> Sent: Thursday, May 10, 2018 12:29 AM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher at intel.com>
> Cc: ehabkost at redhat.com; netdev at vger.kernel.org; jayanth at goubiq.com;
> linux-kernel at vger.kernel.org; Bart.VanAssche at wdc.com;
> postmodern.mod3 at gmail.com; Achim Mildenberger
> <admin at fph.physik.uni-karlsruhe.de>; intel-wired-lan at lists.osuosl.org;
> olouvignes at gmail.com
> Subject: [Intel-wired-lan] [PATCH] e1000e: Ignore TSYNCRXCTL when getting
> I219 clock attributes
> 
> There have been multiple reports of crashes that look like
> kernel: RIP: 0010:[<ffffffff8110303f>] timecounter_read+0xf/0x50
> [...]
> kernel: Call Trace:
> kernel:  [<ffffffffa0806b0f>] e1000e_phc_gettime+0x2f/0x60 [e1000e]
> kernel:  [<ffffffffa0806c5d>] e1000e_systim_overflow_work+0x1d/0x80
> [e1000e]
> kernel:  [<ffffffff810992c5>] process_one_work+0x155/0x440
> kernel:  [<ffffffff81099e16>] worker_thread+0x116/0x4b0
> kernel:  [<ffffffff8109f422>] kthread+0xd2/0xf0
> kernel:  [<ffffffff8163184f>] ret_from_fork+0x3f/0x70
> 
> These can be traced back to the fact that e1000e_systim_reset() skips the
> timecounter_init() call if e1000e_get_base_timinca() returns -EINVAL, which
> leads to a null deref in timecounter_read().
> 
> Commit 83129b37ef35 ("e1000e: fix systim issues", v4.2-rc1) reworked
> e1000e_get_base_timinca() in such a way that it can return -EINVAL for
> e1000_pch_spt if the SYSCFI bit is not set in TSYNCRXCTL.
> 
> Some experimentation has shown that on I219 (e1000_pch_spt, "MAC: 12")
> adapters, the E1000_TSYNCRXCTL_SYSCFI flag is unstable; TSYNCRXCTL reads
> sometimes don't have the SYSCFI bit set. Retrying the read shortly after
> finds the bit to be set. This was observed at boot (probe) but also link up
> and link down.
> 
> Moreover, the phc (PTP Hardware Clock) seems to operate normally even
> after
> reads where SYSCFI=0. Therefore, remove this register read and
> unconditionally set the clock parameters.
> 
> Reported-by: Achim Mildenberger <admin at fph.physik.uni-karlsruhe.de>
> Message-Id: <20180425065243.g5mqewg5irkwgwgv at f2>
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1075876
> Fixes: 83129b37ef35 ("e1000e: fix systim issues")
> Signed-off-by: Benjamin Poirier <bpoirier at suse.com>
> ---
>  drivers/net/ethernet/intel/e1000e/netdev.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)

Tested-by: Aaron Brown <aaron.f.brown at intel.com>