Sometimes it's useful for users of the DP AUX bus (like panels) to be able to poll HPD. Let's add a callback that allows DP AUX busses drivers to provide this.
Suggested-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Signed-off-by: Douglas Anderson dianders@chromium.org Reviewed-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org ---
Changes in v4: - Comments now explain that we may wait longer due to debouncing. - Rebased to handle the fact that the stuct moved files.
Changes in v2: - Change is_hpd_asserted() to wait_hpd_asserted()
include/drm/display/drm_dp_helper.h | 30 +++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+)
diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h index c5f8f45511ed..db0fe9f8a612 100644 --- a/include/drm/display/drm_dp_helper.h +++ b/include/drm/display/drm_dp_helper.h @@ -389,6 +389,36 @@ struct drm_dp_aux { ssize_t (*transfer)(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg);
+ /** + * @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. + * + * This function will efficiently wait for the HPD signal to be + * asserted. The `wait_us` parameter that is passed in says that we + * know that the HPD signal is expected to be asserted within `wait_us` + * microseconds. This function could wait for longer than `wait_us` if + * the logic in the DP controller has a long debouncing time. The + * important thing is that if this function returns success that the + * DP controller is ready to send AUX transactions. + * + * This function returns 0 if HPD was asserted or -ETIMEDOUT if time + * expired and HPD wasn't asserted. This function should not print + * timeout errors to the log. + * + * The semantics of this function are designed to match the + * readx_poll_timeout() function. That means a `wait_us` of 0 means + * to wait forever. Like readx_poll_timeout(), this function may sleep. + * + * NOTE: this function specifically reports the state of the HPD pin + * that's associated with the DP AUX channel. This is different from + * the HPD concept in much of the rest of DRM which is more about + * physical presence of a display. For eDP, for instance, a display is + * assumed always present even if the HPD pin is deasserted. + */ + int (*wait_hpd_asserted)(struct drm_dp_aux *aux, unsigned long wait_us); + /** * @i2c_nack_count: Counts I2C NACKs, used for DP validation. */