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

["Neftin, Sasha" <sasha.neftin@intel.com>]

On 5/10/2018 21:42, Keller, Jacob E wrote:
>> -----Original Message-----
>> From: Benjamin Poirier [mailto:bpoirier@suse.com]
>> Sent: Thursday, May 10, 2018 12:29 AM
>> To: Kirsher, Jeffrey T <jeffrey.t.kirsher@intel.com>
>> Cc: Keller, Jacob E <jacob.e.keller@intel.com>; Achim Mildenberger
>> <admin@fph.physik.uni-karlsruhe.de>; olouvignes@gmail.com;
>> jayanth@goubiq.com; ehabkost@redhat.com; postmodern.mod3@gmail.com;
>> Bart.VanAssche@wdc.com; intel-wired-lan@lists.osuosl.org;
>> netdev@vger.kernel.org; linux-kernel@vger.kernel.org
>> Subject: [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@fph.physik.uni-karlsruhe.de>
>> Message-Id: <20180425065243.g5mqewg5irkwgwgv@f2>
>> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1075876
>> Fixes: 83129b37ef35 ("e1000e: fix systim issues")
>> Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
>> ---
>>   drivers/net/ethernet/intel/e1000e/netdev.c | 15 ++++++---------
>>   1 file changed, 6 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
>> b/drivers/net/ethernet/intel/e1000e/netdev.c
>> index ec4a9759a6f2..3afb1f3b6f91 100644
>> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
>> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
>> @@ -3546,15 +3546,12 @@ s32 e1000e_get_base_timinca(struct e1000_adapter
>> *adapter, u32 *timinca)
>>   		}
>>   		break;
>>   	case e1000_pch_spt:
>> -		if (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI) {
>> -			/* Stable 24MHz frequency */
>> -			incperiod = INCPERIOD_24MHZ;
>> -			incvalue = INCVALUE_24MHZ;
>> -			shift = INCVALUE_SHIFT_24MHZ;
>> -			adapter->cc.shift = shift;
>> -			break;
>> -		}
>> -		return -EINVAL;
>> +		/* Stable 24MHz frequency */
>> +		incperiod = INCPERIOD_24MHZ;
>> +		incvalue = INCVALUE_24MHZ;
>> +		shift = INCVALUE_SHIFT_24MHZ;
>> +		adapter->cc.shift = shift;
>> +		break;
>>   	case e1000_pch_cnp:
>>   		if (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI) {
>>   			/* Stable 24MHz frequency */
>> --
>> 2.16.3
> 
> Given testing showing that the clock operates fine regardless of the register read, I think this is probably fine. Normally I believe the register was used to check which frequency was in use, but it doesn't seem to serve that purpose here.
> 
> Thanks,
> Jake
> _______________________________________________
> Intel-wired-lan mailing list
> Intel-wired-lan@osuosl.org
> https://lists.osuosl.org/mailman/listinfo/intel-wired-lan
> 
I've checked our specification, looks only 24MHz used for this product. 
Hope no different platform with another clock support has been 
distributed. So, let's pick up this change.