From 02d8867abba8f2ad1e0d96ee0b4c33b399ee89a9 Mon Sep 17 00:00:00 2001
From: Douglas Anderson <dianders@chromium.org>
Date: Tue, 14 Jun 2022 14:54:15 -0700
Subject: drm/dp: Add wait_hpd_asserted() callback to struct drm_dp_aux
Git-commit: 841d742f094e00e514627bde65d7822e98fb3e4c
Patch-mainline: v6.0-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225 jsc#PED-2849
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>
Link: https://patchwork.freedesktop.org/patch/msgid/20220614145327.v4.1.Icf57bb12233a47727013c6ab69eebf803e22ebc1@changeid
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
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.
*/
--
2.38.1