Re: [RFC PATCH 2/3] net: macb: Add support for 1588 for Zynq Ultrascale+ MPSoC

Hi Punnaiah,

cpts_match(...) has a way to parse frames, while ptp_classify_raw identifies the underlying protocol (in case the frames are parsed on data path), or tx/rxtstamp callbacks can be used with PTP events. But, there is comment in ptp_classify.h which worries me.

Unfortunately,  I cannot access https://gitenterprise.xilinx.com.

Best regards,
Andrei

On 09.08.2016 18:56, Punnaiah Choudary Kalluri wrote:

Hi Nicolas,

 1588 implementation in cadence GEM IP we have in Zynq Ultascale+ MPSoC is
Different to the one in Zynq SOC.

In earlier version, all timestamp values will be stored in registers and there is no specific
Mechanism to distinguish the received ethernet frame that contains time stamp information
Other than parsing the frame for PTP packet type.

We have basic implementation for earlier version in our out of tree driver, which is going to be deprecated
Soon. You could also check the below driver for 1588 support.
https://gitenterprise.xilinx.com/Linux/linux-xlnx/blob/master/drivers/net/ethernet/xilinx/xilinx_emacps.c


Regards,
Punnaiah

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-----Original Message-----
From: Nicolas Ferre [mailto:nicolas.ferre@atmel.com]
Sent: Tuesday, August 09, 2016 10:10 PM
To: Harini Katakam <redacted>; Harini Katakam
[off-list ref]; Andrei Pistirica [off-list ref]
Cc: davem@davemloft.net; Boris Brezillon <boris.brezillon@free-
electrons.com>; alexandre.belloni@free-electrons.com;
netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
devicetree@vger.kernel.org; Punnaiah Choudary Kalluri
[off-list ref]; Michal Simek [off-list ref]; Anirudha
Sarangi [off-list ref]
Subject: Re: [RFC PATCH 2/3] net: macb: Add support for 1588 for Zynq
Ultrascale+ MPSoC

Le 21/09/2015 à 19:49, Harini Katakam a écrit :

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On Fri, Sep 11, 2015 at 1:27 PM, Harini Katakam
[off-list ref] wrote:

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Cadence GEM in Zynq Ultrascale+ MPSoC supports 1588 and provides a
102 bit time counter with 48 bits for seconds, 30 bits for nsecs and
24 bits for sub-nsecs. The timestamp is made available to the SW through
registers as well as (more precisely) through upper two words in
an extended BD.

This patch does the following:
- Adds MACB_CAPS_TSU in zynqmp_config.
- Registers to ptp clock framework (after checking for timestamp support

in

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  IP and capability in config).
- TX BD and RX BD control registers are written to populate timestamp in
  extended BD words.
- Timer initialization is done by writing time of day to the timer counter.
- ns increment register is programmed as NS_PER_SEC/TSU_CLK.
  For a 24 bit subns precision, the subns increment equals
  remainder of (NS_PER_SEC/TSU_CLK) * (2^24).
  TSU (Time stamp unit) clock is obtained by the  driver from devicetree.
- HW time stamp capabilities are advertised via ethtool and macb ioctl is
  updated accordingly.
- For all PTP event frames, nanoseconds and the lower 5 bits of seconds

are

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  obtained from the BD. This offers a precise timestamp. The upper bits
  (which dont vary between consecutive packets) are obtained from the
  TX/RX PTP event/PEER registers. The timestamp obtained thus is

updated

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  in skb for upper layers to access.
- The drivers register functions with ptp to perform time and frequency
  adjustment.
- Time adjustment is done by writing to the 1558_ADJUST register.
  The controller will read the delta in this register and update the timer
  counter register. Alternatively, for large time offset adjustments,
  the driver reads the secs and nsecs counter values, adds/subtracts the
  delta and updates the timer counter. In order to be as precise as

possible,

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  nsecs counter is read again if secs has incremented during the counter

read.

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- Frequency adjustment is not directly supported by this IP.
  addend is the initial value ns increment and similarly addendesub.
  The ppb (parts per billion) provided is used as
  ns_incr = addend +/- (ppb/rate).
  Similarly the remainder of the above is used to populate subns

increment.

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  In case the ppb requested is negative AND subns adjustment greater

than

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  the addendsub, ns_incr is reduced by 1 and subns_incr is adjusted in
  positive accordingly.

Signed-off-by: Harini Katakam <redacted>:
---
 drivers/net/ethernet/cadence/macb.c |  372

++++++++++++++++++++++++++++++++++-

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 drivers/net/ethernet/cadence/macb.h |   64 ++++++
 2 files changed, 428 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb.c

b/drivers/net/ethernet/cadence/macb.c

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index bb2932c..b531008 100644

--- a/drivers/net/ethernet/cadence/macb.c
+++ b/drivers/net/ethernet/cadence/macb.c

@@ -30,6 +30,8 @@
 #include <linux/of_device.h>
 #include <linux/of_mdio.h>

[..]

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+       unsigned int            ns_incr;
+       unsigned int            subns_incr;
 };

 static inline bool macb_is_gem(struct macb *bp)
--
1.7.9.5

Ping

Thanks.

Harini,

I come back to this patch of last year and I'm sorry about being so late
answering you.

Andrei who is added to the discussion will have some time to deal with
this feature and we would like to make some progress with it. He already
had some work done on his side before I recall your email.

So, could you please re-send your original 1588 patch with Andrei in
copy so that we can all (re-)start the discussion and progress for
adding this feature.

We must also note that some hardware differences between our platforms
may have an impact on the code and how we implement things (as
highlighted on this forum:
http://www.at91.com/discussions/viewtopic.php/f,12/t,25462.html).
Anyway, we'll overcome this and have a widely tested solution at the end
of the day!

Thanks for your patience, bye!

PS: for some reason, I only have this "ping" part of your email but not
the original one
--
Nicolas Ferre

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