linux-kernel - [PATCH] drm/bridge: it6505: Add caching for EDID

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Message-Id: <20221115112720.911158-1-treapking@chromium.org>
Date:   Tue, 15 Nov 2022 19:27:20 +0800
From:   Pin-yen Lin <treapking@...omium.org>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Cc:     allen chen <allen.chen@....com.tw>, linux-kernel@...r.kernel.org,
        David Airlie <airlied@...il.com>,
        dri-devel@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        Pin-yen Lin <treapking@...omium.org>
Subject: [PATCH] drm/bridge: it6505: Add caching for EDID

Add caching when EDID is read, and invalidate the cache until the
bridge detects HPD low or sink count changes on HPD_IRQ.

It takes 1.2s for IT6505 bridge to read a 3-block EDID, and skipping
one EDID read would be a notable difference on user experience.

Signed-off-by: Pin-yen Lin <treapking@...omium.org>

---

 drivers/gpu/drm/bridge/ite-it6505.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index 21a9b8422bda..4b818f31668f 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -457,6 +457,8 @@ struct it6505 {
 
 	/* it6505 driver hold option */
 	bool enable_drv_hold;
+
+	struct edid *cached_edid;
 };
 
 struct it6505_step_train_para {
@@ -2244,6 +2246,13 @@ static void it6505_plugged_status_to_codec(struct it6505 *it6505)
 				   status == connector_status_connected);
 }
 
+
+static void it6505_remove_edid(struct it6505 *it6505)
+{
+	kfree(it6505->cached_edid);
+	it6505->cached_edid = NULL;
+}
+
 static int it6505_process_hpd_irq(struct it6505 *it6505)
 {
 	struct device *dev = &it6505->client->dev;
@@ -2270,6 +2279,7 @@ static int it6505_process_hpd_irq(struct it6505 *it6505)
 		it6505_reset_logic(it6505);
 		it6505_int_mask_enable(it6505);
 		it6505_init(it6505);
+		it6505_remove_edid(it6505);
 		return 0;
 	}
 
@@ -2353,6 +2363,7 @@ static void it6505_irq_hpd(struct it6505 *it6505)
 			it6505_video_reset(it6505);
 	} else {
 		memset(it6505->dpcd, 0, sizeof(it6505->dpcd));
+		it6505_remove_edid(it6505);
 
 		if (it6505->hdcp_desired)
 			it6505_stop_hdcp(it6505);
@@ -3016,16 +3027,18 @@ static struct edid *it6505_bridge_get_edid(struct drm_bridge *bridge,
 {
 	struct it6505 *it6505 = bridge_to_it6505(bridge);
 	struct device *dev = &it6505->client->dev;
-	struct edid *edid;
 
-	edid = drm_do_get_edid(connector, it6505_get_edid_block, it6505);
+	if (!it6505->cached_edid) {
+		it6505->cached_edid = drm_do_get_edid(connector, it6505_get_edid_block,
+						      it6505);
 
-	if (!edid) {
-		DRM_DEV_DEBUG_DRIVER(dev, "failed to get edid!");
-		return NULL;
+		if (!it6505->cached_edid) {
+			DRM_DEV_DEBUG_DRIVER(dev, "failed to get edid!");
+			return NULL;
+		}
 	}
 
-	return edid;
+	return drm_edid_duplicate(it6505->cached_edid);
 }
 
 static const struct drm_bridge_funcs it6505_bridge_funcs = {
@@ -3367,6 +3380,7 @@ static void it6505_i2c_remove(struct i2c_client *client)
 	drm_dp_aux_unregister(&it6505->aux);
 	it6505_debugfs_remove(it6505);
 	it6505_poweroff(it6505);
+	it6505_remove_edid(it6505);
 }
 
 static const struct i2c_device_id it6505_id[] = {
-- 
2.38.1.493.g58b659f92b-goog