Messages in this thread | | | Date | Wed, 7 Dec 2022 12:38:08 +0200 | From | Vladimir Oltean <> | Subject | Re: [Patch net-next v2 07/13] net: dsa: microchip: ptp: add packet reception timestamping |
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On Wed, Dec 07, 2022 at 06:00:27AM +0000, Arun.Ramadoss@microchip.com wrote: > I looked into the sja1105 and hellcreek rxtstamp() implementation. > Here, SKB is queued in rxtstamp() and ptp_schedule_worker is started. > In the work queue, skb is dequeued and current ptp hardware clock is > read. Using the partial time stamp and phc clock, absolute time stamp > is calculated and posted. > In this KSZ implementation, ptp_schedule_worker is used for maintaining > the ptp software clock which read value from hardware clock every > second for faster access of clock value. > > Based on the above observation, I have doubt on how to implement. Below > are the algorithm. Kindly suggest which one to proceed. > 1. Remove the existing ptp software clock mainpulation using > ptp_schedule_worker. Instead in the ptp_schedule_worker, dequeue the > skb and timestamp the rx packets by directly reading from the ptp > hardware clock. > 2. Keep the existing implementation, add the rxtstamp() where it will > not queue skb instead just process the timestamping with using software > clock and KSZ_SKB_CB()->tstamp.
Search more, you'll find felix_rxtstamp() which is closer to (2) and to what you need. There, reading the 64-bit PTP time is done in NET_RX softirq context because the register access is over MMIO. That might change in the future with the introduction of the SPI controlled VSC7512, but for now it is a good example.
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