diff options
| author | Wayne Lin <Wayne.Lin@amd.com> | 2025-01-13 12:10:59 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-04-10 15:37:27 +0300 |
| commit | c3b8e7c6809a5e27437d43c185b0a4e50f68586e (patch) | |
| tree | 3c2de3abff62a822e178883925f90a70bc9a8f2b /include | |
| parent | 8830a2a324c4edeab89694e0d91738b85ccb5e7c (diff) | |
| download | linux-c3b8e7c6809a5e27437d43c185b0a4e50f68586e.tar.xz | |
drm/dp_mst: Fix drm RAD print
[ Upstream commit 6bbce873a9c97cb12f5455c497be279ac58e707f ]
[Why]
The RAD of sideband message printed today is incorrect.
For RAD stored within MST branch
- If MST branch LCT is 1, it's RAD array is untouched and remained as 0.
- If MST branch LCT is larger than 1, use nibble to store the up facing
port number in cascaded sequence as illustrated below:
u8 RAD[0] = (LCT_2_UFP << 4) | LCT_3_UFP
RAD[1] = (LCT_4_UFP << 4) | LCT_5_UFP
...
In drm_dp_mst_rad_to_str(), it wrongly to use BIT_MASK(4) to fetch the port
number of one nibble.
[How]
Adjust the code by:
- RAD array items are valuable only for LCT >= 1.
- Use 0xF as the mask to replace BIT_MASK(4)
V2:
- Document how RAD is constructed (Imre)
V3:
- Adjust the comment for rad[] so kdoc formats it properly (Lyude)
Fixes: 2f015ec6eab6 ("drm/dp_mst: Add sideband down request tracing + selftests")
Cc: Imre Deak <imre.deak@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Lyude Paul <lyude@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250113091100.3314533-2-Wayne.Lin@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/drm/display/drm_dp_mst_helper.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/include/drm/display/drm_dp_mst_helper.h b/include/drm/display/drm_dp_mst_helper.h index 46705dacdd08..7751be9452c1 100644 --- a/include/drm/display/drm_dp_mst_helper.h +++ b/include/drm/display/drm_dp_mst_helper.h @@ -215,6 +215,13 @@ struct drm_dp_mst_branch { */ struct list_head destroy_next; + /** + * @rad: Relative Address of the MST branch. + * For &drm_dp_mst_topology_mgr.mst_primary, it's rad[8] are all 0, + * unset and unused. For MST branches connected after mst_primary, + * in each element of rad[] the nibbles are ordered by the most + * signifcant 4 bits first and the least significant 4 bits second. + */ u8 rad[8]; u8 lct; int num_ports; |