[v6,05/30] drm/bridge: analogix_dp: Wait for HPD signal before configuring link

Message ID 20180405095000.9756-6-enric.balletbo@collabora.com
State New
Headers show
Series
  • DRM Rockchip rk3399 (Kevin)
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Commit Message

Enric Balletbo i Serra April 5, 2018, 9:49 a.m.
From: zain wang <wzz@rock-chips.com>

According to DP spec v1.3 chap 3.5.1.2 Link Training, Link Policy Maker
must first detect that the HPD signal is asserted high by the Downstream
Device before establishing a link with it.

Cc: St├ęphane Marchesin <marcheu@chromium.org>
Signed-off-by: zain wang <wzz@rock-chips.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
---

 drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch

diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
index bf805f156272..3269deec739d 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1169,6 +1169,17 @@  static int analogix_dp_set_bridge(struct analogix_dp_device *dp)
 	if (ret)
 		goto out_dp_init;
 
+	/*
+	 * According to DP spec v1.3 chap 3.5.1.2 Link Training,
+	 * We should first make sure the HPD signal is asserted high by device
+	 * when we want to establish a link with it.
+	 */
+	ret = analogix_dp_detect_hpd(dp);
+	if (ret) {
+		DRM_ERROR("failed to get hpd single ret = %d\n", ret);
+		goto out_dp_init;
+	}
+
 	ret = analogix_dp_commit(dp);
 	if (ret)
 		goto out_dp_init;