Re: [Intel-wired-lan] [PATCH iwl-net v2] igc: Handle PPS start time programming for past time values

["naamax.meir" <naamax.meir@linux.intel.com>]

On 6/15/2023 09:30, aravindhan.gunasekaran@intel.com wrote:
> From: Aravindhan Gunasekaran <aravindhan.gunasekaran@intel.com>
> 
> I225/6 hardware can be programmed to start PPS output once
> the time in Target Time registers is reached. The time
> programmed in these registers should always be into future.
> Only then PPS output is triggered when SYSTIM register
> reaches the programmed value. There are two modes in i225/6
> hardware to program PPS, pulse and clock mode.
> 
> There were issues reported where PPS is not generated when
> start time is in past.
> 
> Example 1, "echo 0 0 0 2 0 > /sys/class/ptp/ptp0/period"
> 
> In the current implementation, a value of '0' is programmed
> into Target time registers and PPS output is in pulse mode.
> Eventually an interrupt which is triggered upon SYSTIM
> register reaching Target time is not fired. Thus no PPS
> output is generated.
> 
> Example 2, "echo 0 0 0 1 0 > /sys/class/ptp/ptp0/period"
> 
> Above case, a value of '0' is programmed into Target time
> registers and PPS output is in clock mode. Here, HW tries to
> catch-up the current time by incrementing Target Time
> register. This catch-up time seem to vary according to
> programmed PPS period time as per the HW design. In my
> experiments, the delay ranged between few tens of seconds to
> few minutes. The PPS output is only generated after the
> Target time register reaches current time.
> 
> In my experiments, I also observed PPS stopped working with
> below test and could not recover until module is removed and
> loaded again.
> 
> 1) echo 0 <future time> 0 1 0 > /sys/class/ptp/ptp1/period
> 2) echo 0 0 0 1 0 > /sys/class/ptp/ptp1/period
> 3) echo 0 0 0 1 0 > /sys/class/ptp/ptp1/period
> 
> After this PPS did not work even if i re-program with proper
> values. I could only get this back working by reloading the
> driver.
> 
> This patch takes care of calculating and programming
> appropriate future time value into Target Time registers.
> 
> Fixes: 5e91c72e560c ("igc: Fix PPS delta between two synchronized end-points")
> Signed-off-by: Aravindhan Gunasekaran <aravindhan.gunasekaran@intel.com>
> ---
> v2: Added Fixes tag
> ---
>   drivers/net/ethernet/intel/igc/igc_ptp.c | 25 +++++++++++++++++++++---
>   1 file changed, 22 insertions(+), 3 deletions(-)

Tested-by: Naama Meir <naamax.meir@linux.intel.com>
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