From: Saeed Mahameed <saeed@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>,
Richard Cochran <richardcochran@gmail.com>
Cc: Eran Ben Elisha <eranbe@nvidia.com>,
"David S. Miller" <davem@davemloft.net>,
netdev@vger.kernel.org, Tariq Toukan <tariqt@nvidia.com>
Subject: Re: [net-next V2 08/15] net/mlx5e: Add TX PTP port object support
Date: Mon, 07 Dec 2020 14:04:51 -0800 [thread overview]
Message-ID: <c989ee2f4ea0ab3f48c1a5774f4ab0eaaeb781c9.camel@kernel.org> (raw)
In-Reply-To: <20201207124233.22540545@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com>
On Mon, 2020-12-07 at 12:42 -0800, Jakub Kicinski wrote:
> On Mon, 7 Dec 2020 07:19:06 -0800 Richard Cochran wrote:
> > On Mon, Dec 07, 2020 at 12:37:45AM -0800, Saeed Mahameed wrote:
> > > we are not adding any new mechanism.
> >
> > Sorry, I didn't catch the beginning of this thread. Are you
> > proposing
> > adding HWTSTAMP_TX_ON_TIME_CRITICAL_ONLY to net_tstamp.h ?
> >
> > If so, then ...
> >
> > > Our driver feature is and internal enhancement yes, but the
> > > suggested
> > > flag is very far from indicating any internal enhancement, is
> > > actually
> > > an enhancement to the current API, and is a very simple extension
> > > with
> > > wide range of improvements to all layers.
> >
> > No, that would be no enhancement but rather a hack for poorly
> > designed
> > hardware.
> >
Why ? how is the new flag different from HWTSTAMP_TX_ONESTEP_SYNC ?
it is a way to fine tune the driver .. nothing is hacky about the new
flag.
> > > Our driver can optimize accuracy when this flag is set, other
> > > drivers
> > > might be happy to implement it since they already have a slow
> > > hw
> >
> > Name three other drivers that would "be happy" to implement
> > this. Can
> > you name even one other?
>
> The behavior is not entirely dissimilar to the time stamps on
> multi-layered devices (e.g. DSA switches). The time stamp can either
> be generated when the packet enters the device (current mlx5
> behavior)
> or when it actually egresses thru the MAC (what this set adds).
>
> So while we could find other hardware like this if we squint hard
> enough
> - I'm not sure how much practical use for CPU-side stamps there is in
> DSA.
>
>
> My main concern is the user friendliness. I think there is no
> question
> that user running ptp4l would want this mlx5 knob to be enabled.
> Would
> we rather see a patch to ptp4l that turns per driver knob or should
> we
> shoot for some form of an API that tells the kernel that we're
> expecting ns level time accuracy?
>
> That's how I would phrase the dilemma here.
This is why i think that the new PTP tx flag to let the driver know
that only PTP EVENT messages are important would be the perfect answer
for all of the above. this flag has a very standard definition, which
could also mean: improved precision for PTP messages if the HW can do
it, why not, ptp4l should always choose this flag if it is present, as
ptp4l shouldn't request ptp hw tstamp on all tx traffic as it is doing
today, it is just an overkill.
other options will be adding knew knob out of the scope of PTP APIs,
which is going to be as ugly as private flag.
next prev parent reply other threads:[~2020-12-07 22:05 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 4:20 [pull request][net-next V2 00/15] mlx5 updates 2020-12-01 Saeed Mahameed
2020-12-03 4:20 ` [net-next V2 01/15] net/mlx5e: Free drop RQ in a dedicated function Saeed Mahameed
2020-12-03 4:20 ` [net-next V2 02/15] net/mlx5e: Allow CQ outside of channel context Saeed Mahameed
2020-12-03 4:20 ` [net-next V2 03/15] net/mlx5e: Allow RQ " Saeed Mahameed
2020-12-03 4:20 ` [net-next V2 04/15] net/mlx5e: Allow SQ " Saeed Mahameed
2020-12-03 4:20 ` [net-next V2 05/15] net/mlx5e: Change skb fifo push/pop API to be used without SQ Saeed Mahameed
2020-12-03 4:20 ` [net-next V2 06/15] net/mlx5e: Split SW group counters update function Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 07/15] net/mlx5e: Move MLX5E_RX_ERR_CQE macro Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 08/15] net/mlx5e: Add TX PTP port object support Saeed Mahameed
2020-12-04 2:29 ` Jakub Kicinski
2020-12-04 19:33 ` Saeed Mahameed
2020-12-04 20:26 ` Jakub Kicinski
2020-12-04 21:57 ` Saeed Mahameed
2020-12-04 22:52 ` Jakub Kicinski
2020-12-05 0:55 ` Vladimir Oltean
2020-12-07 6:22 ` Saeed Mahameed
2020-12-04 23:17 ` Jakub Kicinski
2020-12-04 23:57 ` Saeed Mahameed
2020-12-05 0:24 ` Jakub Kicinski
2020-12-06 13:37 ` Eran Ben Elisha
2020-12-06 17:08 ` Richard Cochran
2020-12-07 8:37 ` Saeed Mahameed
2020-12-07 11:05 ` Eran Ben Elisha
2020-12-07 15:19 ` Richard Cochran
2020-12-07 20:42 ` Jakub Kicinski
2020-12-07 22:04 ` Saeed Mahameed [this message]
2020-12-08 13:02 ` Richard Cochran
2020-12-06 13:36 ` Eran Ben Elisha
2020-12-07 20:29 ` Jakub Kicinski
2020-12-06 13:33 ` Eran Ben Elisha
2020-12-05 1:49 ` Vladimir Oltean
2020-12-05 2:10 ` Jakub Kicinski
2020-12-05 13:20 ` Richard Cochran
2020-12-07 5:50 ` Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 09/15] net/mlx5e: Add TX port timestamp support Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 10/15] net/mlx5e: remove unnecessary memset Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 11/15] net/mlx5e: Remove duplicated include Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 12/15] net/mlx5: Arm only EQs with EQEs Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 13/15] net/mlx5: Fix passing zero to 'PTR_ERR' Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 14/15] net/mlx5e: Split between RX/TX tunnel FW support indication Saeed Mahameed
2020-12-03 4:21 ` [net-next V2 15/15] net/mlx5e: Fill mlx5e_create_cq_param in a function Saeed Mahameed
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