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@xxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
Left Dmitry's Reviewed-by tag off since patch changed enough.
Changes in v2:
- Change is_hpd_asserted() to wait_hpd_asserted()
include/drm/dp/drm_dp_helper.h | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h
index 53d1e722f4de..0940c415db8c 100644
--- a/include/drm/dp/drm_dp_helper.h
+++ b/include/drm/dp/drm_dp_helper.h
@@ -2035,6 +2035,32 @@ 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 up to `wait_us` microseconds
+ * for HPD to be asserted and might sleep.
+ *
+ * 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. If you want to do a quick poll you could pass 1
+ * for `wait_us`.
+ *
+ * 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.
*/
--
2.36.0.rc0.470.gd361397f0d-goog
