[PATCH v4 0/4] drm/dp: Rework LTTPR transparent mode handling and add support to msm driver
Abel Vesa
abel.vesa at linaro.org
Wed Jan 8 14:31:42 UTC 2025
Looking at both i915 and nouveau DP drivers, both are setting the first
LTTPR (if found) in transparent mode first and then in non-transparent
mode, just like the DP v2.0 specification mentions in section 3.6.6.1.
Being part of the standard, setting the LTTPR in a specific operation mode
can be easily moved in the generic framework. So do that by adding a new
helper.
Then, the msm DP driver is lacking any kind of support for LTTPR handling,
so add it by reading the LTTPR caps for figuring out the number of LTTPRs
found on plug detect and then do exactly what the i915 and nouveau drivers
do with respect to toggling through operating modes, just like the
up-mentioned section from DP spec describes.
At some point, link training per sub-segment will probably be needed, but
for now, toggling the operating modes seems to be enough at least for the
X Elite-based platforms that this patchset has been tested on.
Signed-off-by: Abel Vesa <abel.vesa at linaro.org>
---
Changes in v4:
- Picked up Dmitry's and Johan's R-b tags for the drm generic and drm
msm patches.
- Moved the comment about the roll-back to transparent mode inside the
if statement and fixed the typos, like Johan suggested.
- Added more details in the commit message for the i915 changes. Details
about the update that the lttpr_common_caps need w.r.t. rollback to
transparent mode in case of failure.
- Link to v3: https://lore.kernel.org/r/20250103-drm-dp-msm-add-lttpr-transparent-mode-set-v3-0-5c367f4b0763@linaro.org
Changes in v3:
- Picked-up T-b tag from Johan for the drm/dp transparent mode set helper
patch
- Re-worked the return value of the drm/dp transparet mode set helper
- Added some more details about what the values of the lttpr_count arg
is expected to be for the drm_dp_lttpr_init(), like Johan suggested.
- Re-worked the non-transparent mode disable->enable so that the rollback
doesn't happen unless enable failed.
- Picked-up Lyude's R-b tag for the nouveau patch.
- Dropped extra parantesis at the end of the drm_dp_lttpr_init() call in
i915 patch.
- Picked-up Johan's T-b tag for the drm/msm/dp patch.
- Added some error handling and an error message in the
msm_dp_display_lttpr_init(), while dropping the unnecessary lttpr_count
local variable.
- Link to v2: https://lore.kernel.org/r/20241211-drm-dp-msm-add-lttpr-transparent-mode-set-v2-0-d5906ed38b28@linaro.org
Changes in v2:
- Added new wrapper over the set_transparent new helper in order to
move the non-transparent disable and the its enable->disable sequence
mentioned in the DP standard section 3.6.6.1 entirely in the generic
implemetation.
- Switch all 3 drivers to use the new wrapper.
- Fixed the return value of the helper to return 0 on success and
negative value on error.
- Added explanation about the transparent/non-transparent modes into the
msm dp commit message.
- Dropped the condition for non-eDP in msm DP driver since it is allowed
to try to get the number of LTTPRs even on eDP and it will be always
0 anyway.
- Dropped the RFC prefix
- Link to v1: https://lore.kernel.org/r/20241031-drm-dp-msm-add-lttpr-transparent-mode-set-v1-0-cafbb9855f40@linaro.org
---
Abel Vesa (4):
drm/dp: Add helper to set LTTPRs in transparent mode
drm/nouveau/dp: Use the generic helper to control LTTPR transparent mode
drm/i915/dp: Use the generic helper to control LTTPR transparent mode
drm/msm/dp: Add support for LTTPR handling
drivers/gpu/drm/display/drm_dp_helper.c | 62 ++++++++++++++++++++++
.../gpu/drm/i915/display/intel_dp_link_training.c | 24 ++-------
drivers/gpu/drm/msm/dp/dp_display.c | 17 ++++++
drivers/gpu/drm/nouveau/nouveau_dp.c | 17 +-----
include/drm/display/drm_dp_helper.h | 2 +
5 files changed, 88 insertions(+), 34 deletions(-)
---
base-commit: 7b4b9bf203da94fbeac75ed3116c84aa03e74578
change-id: 20241031-drm-dp-msm-add-lttpr-transparent-mode-set-136cd5bfde07
Best regards,
--
Abel Vesa <abel.vesa at linaro.org>
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