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From:   Hsin-Yi Wang <hsinyi@chromium.org>
To:     Chun-Kuang Hu <chunkuang.hu@kernel.org>
Cc:     Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Rex-BC Chen <rex-bc.chen@mediatek.com>,
        Jitao Shi <jitao.shi@mediatek.com>,
        dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: [PATCH] drm/mediatek: mtk-dpi: Set out_fmt from config if not the last bridge
Date:   Mon, 12 Jul 2021 17:46:57 +0800
Message-Id: <20210712094657.1159299-1-hsinyi@chromium.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

atomic_get_output_bus_fmts() is only called when the bridge is the last
element in the bridge chain.

If mtk-dpi is not the last bridge, the format of output_bus_cfg is
MEDIA_BUS_FMT_FIXED, and mtk_dpi_dual_edge() will fail to write correct
value to regs.

Fixes: ec8747c52434 ("drm/mediatek: dpi: Add bus format negotiation")
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
---
 drivers/gpu/drm/mediatek/mtk_dpi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c b/drivers/gpu/drm/mediatek/mtk_dpi.c
index bced555648b01..25c565f9179cc 100644
--- a/drivers/gpu/drm/mediatek/mtk_dpi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
@@ -610,6 +610,10 @@ static int mtk_dpi_bridge_atomic_check(struct drm_bridge *bridge,
 
 	out_bus_format = bridge_state->output_bus_cfg.format;
 
+	if (out_bus_format == MEDIA_BUS_FMT_FIXED)
+		if (dpi->conf->num_output_fmts)
+			out_bus_format = dpi->conf->output_fmts[0];
+
 	dev_dbg(dpi->dev, "input format 0x%04x, output format 0x%04x\n",
 		bridge_state->input_bus_cfg.format,
 		bridge_state->output_bus_cfg.format);
-- 
2.32.0.93.g670b81a890-goog