drm/amd/display: Add retry to read ddc_clock pin

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[ Upstream commit bd4905a958 ]

[WHY]
On customer board, there is one pluse (1v , < 1ms) on
DDC_CLK pin when plug / unplug DP cable. Driver will read
it and config DP to HDMI/DVI dongle.

[HOW]
If there is a real dongle, DDC_CLK should be always pull high.
Try to read again to recovery this special case. Retry times = 3.
Need additional 3ms to detect DP passive dongle(3 failures)

Signed-off-by: Paul Hsieh <paul.hsieh@amd.com>
Reviewed-by: Eric Yang <eric.yang2@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Paul Hsieh 2018-11-22 18:43:45 +08:00 • committed by Greg Kroah-Hartman

parent 368aa93b49

commit 9c77d1a531

1 changed files with 17 additions and 6 deletions

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drivers/gpu/drm/amd/display/dc/core/dc_link.c

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