Commit 841d742f authored by Douglas Anderson's avatar Douglas Anderson
Browse files

drm/dp: Add wait_hpd_asserted() callback to struct drm_dp_aux 



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: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Reviewed-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220614145327.v4.1.Icf57bb12233a47727013c6ab69eebf803e22ebc1@changeid
parent 15b9ca16

include/drm/display/drm_dp_helper.h

+30 −0
Original line number Diff line number Diff line
@@ -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.

	 */