net: dsa: sja1105: Take PTP egress timestamp by port, not mgmt slot
The PTP egress timestamp N must be captured from register PTPEGR_TS[n], where n = 2 * PORT + TSREG. There are 10 PTPEGR_TS registers, 2 per port. We are only using TSREG=0. As opposed to the management slots, which are 4 in number (SJA1105_NUM_PORTS, minus the CPU port). Any management frame (which includes PTP frames) can be sent to any non-CPU port through any management slot. When the CPU port is not the last port (#4), there will be a mismatch between the slot and the port number. Luckily, the only mainline occurrence with this switch (arch/arm/boot/dts/ls1021a-tsn.dts) does have the CPU port as #4, so the issue did not manifest itself thus far. Fixes: 47ed985e ("net: dsa: sja1105: Add logic for TX timestamping") Signed-off-by: Vladimir Oltean <olteanv@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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