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drm: Change limited M/N quirk to constant N quirk.

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Some DP dongles in particular seem to be fussy about too large
link M/N values. Set specific value for N divider can resolve
this issue per dongle vendor's comment. So configure N as
constant value (0x8000) to instead of reduce M/N formula when
specific DP dongle connected.

v2: add more comments for issue description and fix typo.
v3: add lost commit messages back for version 2
v4: send patch to both intel-gfx and dri-devel

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Cooper Chiou <cooper.chiou@intel.com>
Cc: Matt Atwood <matthew.s.atwood@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Clint Taylor <clinton.a.taylor@intel.com>
Tested-by: Clint Taylor <clinton.a.taylor@intel.com>
Signed-off-by: Lee, Shawn C <shawn.c.lee@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1536733371-25004-3-git-send-email-shawn.c.lee@intel.com
This commit is contained in:
Lee, Shawn C
2018-09-11 23:22:50 -07:00
committed by Jani Nikula
parent 0b49bbbd9f
commit 53ca2edcf0
6 changed files with 25 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
include/drm/drm_dp_helper.h
View File

@ -1261,12 +1261,12 @@ int drm_dp_read_desc(struct drm_dp_aux *aux, struct drm_dp_desc *desc,
*/
enum drm_dp_quirk {
/**
* @DP_DPCD_QUIRK_LIMITED_M_N:
* @DP_DPCD_QUIRK_CONSTANT_N:
*
* The device requires main link attributes Mvid and Nvid to be limited
* to 16 bits.
* to 16 bits. So will give a constant value (0x8000) for compatability.
*/
DP_DPCD_QUIRK_LIMITED_M_N,
DP_DPCD_QUIRK_CONSTANT_N,
};
/**