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From: Wojciech Macek <wmacek@chromium.org>
To: Chun-Kuang Hu <chunkuang.hu@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	David Airlie <airlied@gmail.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>,
	dri-devel@lists.freedesktop.org,
	linux-mediatek@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	chrome-platform@lists.linux.dev
Cc: Wojciech Macek <wmacek@chromium.org>
Subject: [PATCH v2] drm/mediatek/dp: fix mtk_dp_aux_transfer return value
Date: Wed, 17 Apr 2024 10:38:19 +0000
Message-ID: <20240417103819.990512-1-wmacek@chromium.org>
Precedence: bulk
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In case there is no DP device attached to the port the
transfer function should return IO error, similar to what
other drivers do.
In case EAGAIN is returned then any read from /dev/drm_dp_aux
device ends up in an infinite loop as the upper layers
constantly repeats the transfer request.

Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
Signed-off-by: Wojciech Macek <wmacek@chromium.org>
---
Changelog v2-v1:
 - added "Fixes" tag
 - corrected e-mail address

V1: https://patchwork.kernel.org/project/linux-mediatek/patch/20240402071113.3135903-1-wmacek@chromium.org/
 drivers/gpu/drm/mediatek/mtk_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 0ba72102636a..536366956447 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -2104,7 +2104,7 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 
 	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP &&
 	    !mtk_dp->train_info.cable_plugged_in) {
-		ret = -EAGAIN;
+		ret = -EIO;
 		goto err;
 	}
 
-- 
2.44.0.683.g7961c838ac-goog