[PATCH v2 3/3] drm/mediatek: Adjust bandwidth limit for DP

[Liankun Yang]

By adjusting the order of link training and relocating it to HPD,
link training can identify the usability of each lane in the current link.

It also supports handling signal instability and weakness due to
environmental issues, enabling the acquisition of a stable bandwidth
for the current link. Subsequently, DP work can proceed based on
the actual maximum bandwidth.

It should training in the hpd event thread.
Check the mode with lane count and link rate of training.

Signed-off-by: Liankun Yang <liankun.yang at mediatek.com>
---
- Adjust DP training timing.
- Adjust parse capabilities timing.
- Add power on/off for connect/disconnect
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 37 +++++++++++++++++--------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index ae4807823a5c..e87f6f52bcce 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1873,6 +1873,7 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
 	struct mtk_dp *mtk_dp = dev;
 	unsigned long flags;
 	u32 status;
+	int ret;
 
 	if (mtk_dp->need_debounce && mtk_dp->train_info.cable_plugged_in)
 		msleep(100);
@@ -1891,9 +1892,28 @@ static irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
 			memset(&mtk_dp->info.audio_cur_cfg, 0,
 			       sizeof(mtk_dp->info.audio_cur_cfg));
 
+			mtk_dp->enabled = false;
+			/* power off aux */
+			mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
+			       DP_PWR_STATE_BANDGAP_TPLL,
+			       DP_PWR_STATE_MASK);
+
 			mtk_dp->need_debounce = false;
 			mod_timer(&mtk_dp->debounce_timer,
 				  jiffies + msecs_to_jiffies(100) - 1);
+		} else {
+			mtk_dp_aux_panel_poweron(mtk_dp, true);
+
+			ret = mtk_dp_parse_capabilities(mtk_dp);
+			if (ret)
+				drm_err(mtk_dp->drm_dev, "Can't parse capabilities\n");
+
+			/* Training */
+			ret = mtk_dp_training(mtk_dp);
+			if (ret)
+				drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
+
+			mtk_dp->enabled = true;
 		}
 	}
 
@@ -2060,16 +2080,6 @@ static const struct drm_edid *mtk_dp_edid_read(struct drm_bridge *bridge,
 
 	drm_edid = drm_edid_read_ddc(connector, &mtk_dp->aux.ddc);
 
-	/*
-	 * Parse capability here to let atomic_get_input_bus_fmts and
-	 * mode_valid use the capability to calculate sink bitrates.
-	 */
-	if (mtk_dp_parse_capabilities(mtk_dp)) {
-		drm_err(mtk_dp->drm_dev, "Can't parse capabilities\n");
-		drm_edid_free(drm_edid);
-		drm_edid = NULL;
-	}
-
 	if (drm_edid) {
 		/*
 		 * FIXME: get rid of drm_edid_raw()
@@ -2263,13 +2273,6 @@ static void mtk_dp_bridge_atomic_enable(struct drm_bridge *bridge,
 
 	mtk_dp_aux_panel_poweron(mtk_dp, true);
 
-	/* Training */
-	ret = mtk_dp_training(mtk_dp);
-	if (ret) {
-		drm_err(mtk_dp->drm_dev, "Training failed, %d\n", ret);
-		goto power_off_aux;
-	}
-
 	ret = mtk_dp_video_config(mtk_dp);
 	if (ret)
 		goto power_off_aux;
-- 
2.45.2