Since eDP panels are not removable it is safe to cache the EDID:
this will avoid a relatively long read transaction at every PM
resume that is unnecessary only in the "special" case of eDP,
hence speeding it up a little, as from now on, as resume operation,
we will perform only link training.

Signed-off-by: AngeloGioacchino Del Regno 
<angelogioacchino.delre...@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c 
b/drivers/gpu/drm/mediatek/mtk_dp.c
index 1f94fcc144d3..84f82cc68672 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -118,6 +118,7 @@ struct mtk_dp {
        const struct mtk_dp_data *data;
        struct mtk_dp_info info;
        struct mtk_dp_train_info train_info;
+       struct edid *edid;
 
        struct platform_device *phy_dev;
        struct phy *phy;
@@ -1993,7 +1994,11 @@ static struct edid *mtk_dp_get_edid(struct drm_bridge 
*bridge,
                usleep_range(2000, 5000);
        }
 
-       new_edid = drm_get_edid(connector, &mtk_dp->aux.ddc);
+       /* eDP panels aren't removable, so we can return a cached EDID. */
+       if (mtk_dp->edid && mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP)
+               new_edid = drm_edid_duplicate(mtk_dp->edid);
+       else
+               new_edid = drm_get_edid(connector, &mtk_dp->aux.ddc);
 
        /*
         * Parse capability here to let atomic_get_input_bus_fmts and
@@ -2022,6 +2027,10 @@ static struct edid *mtk_dp_get_edid(struct drm_bridge 
*bridge,
                drm_atomic_bridge_chain_post_disable(bridge, 
connector->state->state);
        }
 
+       /* If this is an eDP panel and the read EDID is good, cache it for 
later */
+       if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP && !mtk_dp->edid && 
new_edid)
+               mtk_dp->edid = drm_edid_duplicate(new_edid);
+
        return new_edid;
 }
 
-- 
2.40.0

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