net: fec: ptp: fix convergence issue to support LinuxPTP stack
iMX6SX IEEE 1588 module has one hw issue in capturing the ATVR register. The current SW flow is: ENET0->ATCR |= ENET_ATCR_CAPTURE_MASK; ts_counter_ns = ENET0->ATVR; The ATVR value is not expected value that cause LinuxPTP stack cannot be convergent. ENET Block Guide/ Chapter for the iMX6SX (PELE) address the issue: After set ENET_ATCR[Capture], there need some time cycles before the counter value is capture in the register clock domain. The wait-time-cycles is at least 6 clock cycles of the slower clock between the register clock and the 1588 clock. So need something like: ENET0->ATCR |= ENET_ATCR_CAPTURE_MASK; wait(); ts_counter_ns = ENET0->ATVR; For iMX6SX, the 1588 ts_clk is fixed to 25Mhz, register clock is 66Mhz, so the wait-time-cycles must be greater than 240ns (40ns * 6). The patch add 1us delay before cpu read ATVR register. Changes V2: Modify the commit/comments log to describe the issue clearly. Signed-off-by:Fugang Duan <B38611@freescale.com> Acked-by:
Richard Cochran <richardcochran@gmail.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
parent
001586a7
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