Merge branch 'net-macb-rework-hardware-timestamp-configuration'

Kim Wooseok via says:

====================
net: macb: Rework hardware timestamp configuration

This started with two problems I found while using PTP hardware
timestamping on a Raspberry Pi 5. A rejected RX filter could still
change the TX one-step setting, and the PTPv1 Sync and Delay_Req filters
returned success without enabling RX timestamps.

This series reworks gem_set_hwtst() to validate the whole request before
programming the hardware. It calculates the settings locally, then
updates the registers and saved configuration under bp->lock. With the
register writes now in the setter, the two helpers are no longer needed.

The remaining patches use the existing ALL fallback for the specific
PTPv1 filters and clear SRTSM when switching away from a PTPv2 filter.
Each change is kept in its own patch.

For v1, I compared the old and new behavior on the Pi 5. When I
requested a TX mode change together with an invalid RX filter, the
patched driver rejected the request without changing the saved settings
or NCR. I also checked transitions between PTPv2 RX and the other
receive filters. SRTSM followed the selected RX filter without changing
unrelated NCR bits.

For the PTPv1 filters, I checked the effect by sending Sync and Delay_Req
packets over Ethernet. Before the change, the packets arrived without
hardware timestamps. With the patches, the driver returned ALL and I
could read the hardware timestamps from the received packets. PTPv2
multicast reception continued to provide hardware timestamps, and
selecting NONE disabled timestamping. I ran these tests with the changes
backported to the Pi's existing Linux 6.18.46 RT kernel.
====================

Link: https://patch.msgid.link/20260923-macb-hwtstamp-rework-v2-0-75c909b2676d@khu.ac.kr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>