[Intel-wired-lan] [PATCH v3 net-next] ice: Add low latency Tx timestamp read

[Michalik, Michal]

Hi Gurucharan,

I don't see Karol answer anywhere - if you already get the response please
excuse me for creating confusion. My input inline below.

BR,
M^2

> 
> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces at osuosl.org> On Behalf Of G, GurucharanX
> Sent: Friday, August 12, 2022 4:24 PM
> To: Kolacinski, Karol <karol.kolacinski at intel.com>; intel-wired-lan at lists.osuosl.org
> Cc: Kolacinski, Karol <karol.kolacinski at intel.com>
> Subject: Re: [Intel-wired-lan] [PATCH v3 net-next] ice: Add low latency Tx timestamp read
> 
> 
> 
> > -----Original Message-----
> > From: Intel-wired-lan <intel-wired-lan-bounces at osuosl.org> On Behalf Of
> > Karol Kolacinski
> > Sent: Tuesday, August 2, 2022 8:28 PM
> > To: intel-wired-lan at lists.osuosl.org
> > Cc: Kolacinski, Karol <karol.kolacinski at intel.com>
> > Subject: [Intel-wired-lan] [PATCH v3 net-next] ice: Add low latency Tx
> > timestamp read
> > 
> > E810 products can support low latency Tx timestamp register read.
> > This requires usage of threaded IRQ instead of kthread to reduce the kthread
> > start latency (spikes up to 20 ms).
> > Add a check for the device capability and use the new method if supported.
> > 
> > Signed-off-by: Karol Kolacinski <karol.kolacinski at intel.com>
> > ---
> 
> If the tx_timestamp_timeout < 15ms then we are observing the send sync failed messages as below. 
> 
> ptp4l 47370.160 timed out while polling for tx timestamp
> ptp4l 47370.160 increasing tx_timestamp_timeout may correct this issue, but it is likely caused by a driver bug
> ptp4l 47370.160 port 2: send sync failed
> 
> But PTP applications require reliable low latency timestamps <10 ms

Agree - this patch enable low latency TX read below 10ms, but in order to
satisfy this requirement you need latest firmware (supporting ts_ll_read
feature). If firmware does not support it we fallback to "old way" of reading
timestamp, which may spike up to ~70ms. Feel free to contact me for any details,
since Karol would be out of the office for next 2 weeks.

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