linux-kernel - [PATCH v5 09/10] drm/mediatek: dp: Add .wait_hpd

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Date:   Thu, 13 Jul 2023 11:01:51 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     chunkuang.hu@...nel.org
Cc:     p.zabel@...gutronix.de, airlied@...il.com, daniel@...ll.ch,
        matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kernel@...labora.com,
        wenst@...omium.org, nfraprado@...labora.com
Subject: [PATCH v5 09/10] drm/mediatek: dp: Add .wait_hpd_asserted() for AUX bus

In order to support usecases in which the panel regulator can be
switched on and off to save power, and usecases in which the panel
regulator is off at boot, add a .wait_hpd_asserted() callback for
the AUX bus: this will make sure to wait until the panel is fully
ready after power-on before trying to communicate with it.

Also, parse the eDP display capabilities in that callback, so that
we can also avoid using the .get_edid() callback from this bridge.

Since at this point the hpd machinery is performed in the new hpd
callback and the detection and edid reading are done outside of
this driver, assign the DRM_BRIDGE_OP_{DETECT, EDID, HPD} ops only
if we're probing full DisplayPort and not eDP.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 8668ab17135d..a00bf6693b28 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1915,6 +1915,29 @@ static irqreturn_t mtk_dp_hpd_event(int hpd, void *dev)
 	return IRQ_WAKE_THREAD;
 }
 
+static int mtk_dp_wait_hpd_asserted(struct drm_dp_aux *mtk_aux, unsigned long wait_us)
+{
+	struct mtk_dp *mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
+	u32 val;
+	int ret;
+
+	ret = regmap_read_poll_timeout(mtk_dp->regs, MTK_DP_TRANS_P0_3414,
+				       val, !!(val & HPD_DB_DP_TRANS_P0_MASK),
+				       wait_us / 100, wait_us);
+	if (ret)
+		return ret;
+
+	mtk_dp->train_info.cable_plugged_in = true;
+
+	ret = mtk_dp_parse_capabilities(mtk_dp);
+	if (ret) {
+		drm_err(mtk_dp->drm_dev, "Can't parse capabilities\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 static int mtk_dp_dt_parse(struct mtk_dp *mtk_dp,
 			   struct platform_device *pdev)
 {
@@ -2564,6 +2587,7 @@ static int mtk_dp_probe(struct platform_device *pdev)
 	mtk_dp->aux.name = "aux_mtk_dp";
 	mtk_dp->aux.dev = dev;
 	mtk_dp->aux.transfer = mtk_dp_aux_transfer;
+	mtk_dp->aux.wait_hpd_asserted = mtk_dp_wait_hpd_asserted;
 	drm_dp_aux_init(&mtk_dp->aux);
 
 	spin_lock_init(&mtk_dp->irq_thread_lock);
@@ -2596,11 +2620,12 @@ static int mtk_dp_probe(struct platform_device *pdev)
 
 	mtk_dp->bridge.funcs = &mtk_dp_bridge_funcs;
 	mtk_dp->bridge.of_node = dev->of_node;
-
-	mtk_dp->bridge.ops =
-		DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_HPD;
 	mtk_dp->bridge.type = mtk_dp->data->bridge_type;
 
+	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP)
+		mtk_dp->bridge.ops = DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID |
+				     DRM_BRIDGE_OP_HPD;
+
 	devm_drm_bridge_add(dev, &mtk_dp->bridge);
 
 	mtk_dp->need_debounce = true;
-- 
2.40.1