phy: lynx-28g: truly power the lanes up or down

phy: lynx-28g: truly power the lanes up or down

The current procedure for power_off() and power_on() is the same as the
one used for major lane reconfiguration, aka halting. But this is
incorrect.

One would expect that a powered off lane causes the CDR (clock and data
recovery) loop of the link partner to lose lock onto its RX stream
(which suggests there are no longer any bit transitions => the channel
is inactive). However, it can be observed that this does not take place
(the CDR lock is still there), which means that a halted lane is not
powered off.

Implement the procedure mentioned in the block guide for powering down
a lane, and then back on. This means:

- lynx_28g_power_off() currently emits a HLT_REQ and waits for it to
  clear. Rename it to lynx_28g_lane_halt() and keep using it for
  lynx_28g_set_mode().
- lynx_28g_power_on() currently emits a RST_REQ and waits for it to
  clear. This is the reset procedure - rename it to
  lynx_28g_lane_reset(), and keep using it for lynx_28g_set_mode().

The "real" lynx_28g_power_off() should emit a STP_REQ and wait for it to
clear. And the "real" lynx_28g_power_on() should clear the DIS bit and
then perform a lane reset. Hook these methods to the phy_ops ::
power_off() and power_on() instead.

As opposed to lynx_28g_power_off() which is also directly hooked to the
PHY API, lynx_28g_lane_halt() isn't; just to lynx_28g_set_mode(), and
the call is being made in a state where we haven't yet made any change
to the lane. So it does make some limited amount of sense to code this
up such that if it fails, we make an attempt to reset the lane anyway
and let the consumer know that phy_set_mode_ext() failed.

Sort the field definitions in LNaTRSTCTL and LNaRRSTCTL in descending
order, and add new definitions for STP_REQ and DIS, previously unused.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20260321011451.1557091-3-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>