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From:   Alexandre Mergnat <amergnat@baylibre.com>
Date:   Mon, 23 Oct 2023 16:40:13 +0200
Subject: [PATCH 13/18] drm/mediatek: dsi: Improves the DSI lane setup
 robustness
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To:     Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Jitao Shi <jitao.shi@mediatek.com>,
        Xinlei Lee <xinlei.lee@mediatek.com>,
        CK Hu <ck.hu@mediatek.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>
Cc:     dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-pwm@vger.kernel.org,
        Alexandre Mergnat <amergnat@baylibre.com>
Precedence: bulk

Currently, mtk_dsi_lane_ready (which setup the DSI lane) is triggered
before mtk_dsi_poweron. lanes_ready flag toggle to true during
mtk_dsi_lane_ready function, and the DSI module is set up during
mtk_dsi_poweron.

Later, during panel driver init, mtk_dsi_lane_ready is triggered but does
nothing because lanes are considered ready. Unfortunately, when the panel
driver try to communicate, the DSI returns a timeout.

The solution found here is to put lanes_ready flag to false after the DSI
module setup into mtk_dsi_poweron to init the DSI lanes after the power /
setup of the DSI module.

Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index d8bfc2cce54d..81cf0ddcc399 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -668,6 +668,8 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
 	mtk_dsi_config_vdo_timing(dsi);
 	mtk_dsi_set_interrupt_enable(dsi);
 
+	dsi->lanes_ready = false;
+
 	return 0;
 err_disable_engine_clk:
 	clk_disable_unprepare(dsi->engine_clk);

-- 
2.25.1