Convert many printk calls to DRM_DEBUG calls to reduce kernel log noise
for normal activities. Switch other printk calls to DRM_ERROR or DRM_INFO.
Signed-off-by: NKeith Packard <keithp@keithp.com>
Signed-off-by: NEric Anholt <eric@anholt.net>

The display port aux channel clock is taken from the hrawclk value, which is
provided to the chip as the FSB frequency (as far as I can determine). The
strapping values for that are available in the CLKCFG register, now used to
select an appropriate divider to generate a 2MHz clock.

In addition, the DisplayPort spec requires that each aux channel I/O be
retried 'at least 3 times' in case the sink is idle when the first request
comes in.
Signed-off-by: NKeith Packard <keithp@keithp.com>

Use distinct error return values for each kind of aux channel I/O failure.
Signed-off-by: NKeith Packard <keithp@keithp.com>

When a DP monitor is plugged back in, it needs to be retrained if it was
active before.
Signed-off-by: NKeith Packard <keithp@keithp.com>

Signed-off-by: NKeith Packard <keithp@keithp.com>