diff options
| author | Val Packett <val@packett.cool> | 2025-07-06 17:42:24 -0300 |
|---|---|---|
| committer | Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com> | 2025-08-21 13:41:59 +0300 |
| commit | 4aa8961b1b9c7498550b41168a91cf1558133dd3 (patch) | |
| tree | 60a57c5ce52e3a2141f4a690b390cf185fd26bb5 | |
| parent | 043d9c6928b010be7902a01b5cdfa7d754535b1a (diff) | |
drm/dp: drm_edp_backlight_set_level: do not always send 3-byte commands
At least some panels using the LSB register are not happy with the
unconditional increase of the command buffer to 3 bytes.
With the BOE NE14QDM in my Dell Latitude 7455, the recent patches for
luminance based brightness have introduced a regression: the brightness
range stopped being contiguous and became nonsensical (it probably was
interpreting the last 2 bytes of the buffer and not the first 2).
Change from using a fixed sizeof() to a length variable that's only
set to 3 when luminance is used. Let's leave the default as 2 even for
the single-byte version, since that's how it worked before.
Fixes: f2db78e37fe7 ("drm/dp: Modify drm_edp_backlight_set_level")
Signed-off-by: Val Packett <val@packett.cool>
Tested-by: Abel Vesa <abel.vesa@linaro.org>
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Link: https://lore.kernel.org/r/20250706204446.8918-1-val@packett.cool
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
| -rw-r--r-- | drivers/gpu/drm/display/drm_dp_helper.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index 1ecc3df7e316..4aaeae4fa03c 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -3962,6 +3962,7 @@ int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct drm_edp_bac int ret; unsigned int offset = DP_EDP_BACKLIGHT_BRIGHTNESS_MSB; u8 buf[3] = { 0 }; + size_t len = 2; /* The panel uses the PWM for controlling brightness levels */ if (!(bl->aux_set || bl->luminance_set)) @@ -3974,6 +3975,7 @@ int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct drm_edp_bac buf[1] = (level & 0x00ff00) >> 8; buf[2] = (level & 0xff0000) >> 16; offset = DP_EDP_PANEL_TARGET_LUMINANCE_VALUE; + len = 3; } else if (bl->lsb_reg_used) { buf[0] = (level & 0xff00) >> 8; buf[1] = (level & 0x00ff); @@ -3981,7 +3983,7 @@ int drm_edp_backlight_set_level(struct drm_dp_aux *aux, const struct drm_edp_bac buf[0] = level; } - ret = drm_dp_dpcd_write_data(aux, offset, buf, sizeof(buf)); + ret = drm_dp_dpcd_write_data(aux, offset, buf, len); if (ret < 0) { drm_err(aux->drm_dev, "%s: Failed to write aux backlight level: %d\n", |