phy: lynx-28g: use timeouts when waiting for lane halt and reset

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There are various circumstances in which a lane halt, or a lane reset,
will fail to complete. If this happens, it will hang the kernel, which
only implements a busy loop with no timeout.

The circumstances in which this will happen are all bugs in nature:
- if we try to power off a powered off lane
- if we try to power off a lane that uses a PLL locked onto the wrong
  refclk frequency (wrong RCW, but SoC boots anyway)

Actually, unbounded loops in the kernel are a bad practice, so let's use
read_poll_timeout() with a custom function that reads both LNaTRSTCTL
(lane transmit control register) and LNaRRSTCTL (lane receive control
register) and returns true when the request is done in both directions.

The HLT_REQ bit has to clear, whereas the RST_DONE bit has to get set.

Any time such an error happens, it is catastrophic and there is no point
in trying to propagate it to our callers:
- if lynx_28g_set_mode() -> lynx_28g_power_on() times out, we have
  already reconfigured the lane, but returning an error would tell the
  caller that we didn't
- if lynx_28g_power_off() times out, again not much for the consumer to
  do to help get out of this situation - the phy_power_off() call is
  probably made from a context that the consumer can't cancel, or it is
  making it to return to a known state from a previous failure.

So just print an error if timeouts happen and let the driver control
flow continue. The entire point is just to not let the kernel freeze.

Suggested-by: Josua Mayer <josua@solid-run.com>
Link: https://lore.kernel.org/lkml/d0c8bbf8-a0c5-469f-a148-de2235948c0f@solid-run.com/
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20260321011451.1557091-2-vladimir.oltean@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

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This commit is contained in:

Vladimir Oltean 2026-03-21 03:14:49 +02:00 • committed by Vinod Koul

parent a62bfbcf2d

commit 905780855a

1 changed files with 56 additions and 16 deletions

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drivers/phy/freescale/phy-fsl-lynx-28g.c

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