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

[Harini Katakam]

Hi Nicolas,

Thanks for your reply

On Tue, Aug 9, 2016 at 10:26 PM, Punnaiah Choudary Kalluri
<punnaiah.choudary.kalluri@xxxxxxxxxx> 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
>
>> -----Original Message-----
>> From: Nicolas Ferre [mailto:nicolas.ferre@xxxxxxxxx]
>> Sent: Tuesday, August 09, 2016 10:10 PM
>> To: Harini Katakam <harinikatakamlinux@xxxxxxxxx>; Harini Katakam
>> <harinik@xxxxxxxxxx>; Andrei Pistirica <Andrei.Pistirica@xxxxxxxxxxxxx>
>> Cc: davem@xxxxxxxxxxxxx; Boris Brezillon <boris.brezillon@free-
>> electrons.com>; alexandre.belloni@xxxxxxxxxxxxxxxxxx;
>> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
>> devicetree@xxxxxxxxxxxxxxx; Punnaiah Choudary Kalluri
>> <punnaia@xxxxxxxxxx>; Michal Simek <michals@xxxxxxxxxx>; Anirudha
>> Sarangi <anirudh@xxxxxxxxxx>
>> Subject: Re: [RFC PATCH 2/3] net: macb: Add support for 1588 for Zynq
>> Ultrascale+ MPSoC
>>
>> Le 21/09/2015 Ã 19:49, Harini Katakam a Ãcrit :
>> > On Fri, Sep 11, 2015 at 1:27 PM, Harini Katakam
>> > <harini.katakam@xxxxxxxxxx> wrote:
>> >> 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
>> >>   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
>> >>   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
>> >>   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,
>> >>   nsecs counter is read again if secs has incremented during the counter
>> read.
>> >> - 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.
>> >>   In case the ppb requested is negative AND subns adjustment greater
>> than
>> >>   the addendsub, ns_incr is reduced by 1 and subns_incr is adjusted in
>> >>   positive accordingly.
>> >>
>> >> Signed-off-by: Harini Katakam <harinik@xxxxxxxxxx>:
>> >> ---
>> >>  drivers/net/ethernet/cadence/macb.c |  372
>> ++++++++++++++++++++++++++++++++++-
>> >>  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
>> >> 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>
>>
>> [..]
>>
>> >> +       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).

Sure, I'm looking into the differences pointed out here.
Of those, I'm going to fix the clk source issue by using the clock framework.
But there are wide differences related to extended BD and indication for
presence of timestamp between different versions of this IP.
As Punnaiah pointed out above, Zynq had a completely different solution.

>> Anyway, we'll overcome this and have a widely tested solution at the end
>> of the day!
>>

Thanks. Yes, I'll send out a patch for the Zynq MPSoC version I'm using
and it can be extended.

Regards,
Harini