regmap_read_poll_timeout() relies on usleep_range() to time the polling
loop. With the current, rather large, scheduling interval, a short
usleep_range() may take a lot longer than expected, causing performance
issues.
Switch the driver over to using regmap_read_poll_timeout_atomic(), which
uses udelay() to time the polling loop.
For comparision, the 'ethtool -m <dev>' command is about 10 times faster
with the atomic variant.
Using 'perf -r10 ethtool -m lan25':
- Driver using regmap_read_poll_timeout():
2.0117 +- 0.0118 seconds time elapsed ( +- 0.58% )
- Driver using regmap_read_poll_timeout_atomic():
0.1674 +- 0.0250 seconds time elapsed ( +- 14.95% )
Signed-off-by: Sander Vanheule <sander@svanheule.net>
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