diff options
| -rw-r--r-- | include/drm/display/drm_dp_helper.h | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h index a62fcd051d4d..6c6a96496df6 100644 --- a/include/drm/display/drm_dp_helper.h +++ b/include/drm/display/drm_dp_helper.h @@ -422,7 +422,18 @@ struct drm_dp_aux { * @wait_hpd_asserted: wait for HPD to be asserted * * This is mainly useful for eDP panels drivers to wait for an eDP - * panel to finish powering on. This is an optional function. + * panel to finish powering on. It is optional for DP AUX controllers + * to implement this function. It is required for DP AUX endpoints + * (panel drivers) to call this function after powering up but before + * doing AUX transfers unless the DP AUX endpoint driver knows that + * we're not using the AUX controller's HPD. One example of the panel + * driver not needing to call this is if HPD is hooked up to a GPIO + * that the panel driver can read directly. + * + * If a DP AUX controller does not implement this function then it + * may still support eDP panels that use the AUX controller's built-in + * HPD signal by implementing a long wait for HPD in the transfer() + * callback, though this is deprecated. * * This function will efficiently wait for the HPD signal to be * asserted. The `wait_us` parameter that is passed in says that we |