linux-kernel - [PATCH v4 11/15] drm/mediatek: dsi: Improves the DSI lane setup robustness

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Message-Id: <20231023-display-support-v4-11-ed82eb168fb1@baylibre.com>
Date: Thu, 23 May 2024 14:49:24 +0200
From: Alexandre Mergnat <amergnat@...libre.com>
To: Chun-Kuang Hu <chunkuang.hu@...nel.org>, 
 Philipp Zabel <p.zabel@...gutronix.de>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Matthias Brugger <matthias.bgg@...il.com>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
 Jitao Shi <jitao.shi@...iatek.com>, CK Hu <ck.hu@...iatek.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org, 
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, 
 Alexandre Mergnat <amergnat@...libre.com>
Subject: [PATCH v4 11/15] drm/mediatek: dsi: Improves the DSI lane setup
 robustness

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@...libre.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 e036d9394c23..cb546a9e9419 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -643,6 +643,8 @@ 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