[PATCH 7.1.y 2/2] drm/mediatek: mtk_dsi: Enable HS clock only at pre-enable

From: AngeloGioacchino Del Regno <[email protected]>

[ Upstream commit 3e191eddbdcb8bf7beb1e9b58209073bd5450719 ]

Commit 76255024cadb ("drm/mediatek: mtk_dsi: enable hs clock
during pre-enable") rightfully moves the HS clock enablement to
before atomic_enable(), but it's moving it to mtk_dsi_poweron(),
which is not only called in the .atomic_pre_enable() callback
for the DRM bridge, but also in the MediaTek DRM's .ddp_start()
callback, which happens way before the bridge ones.

The HS clock enablement should be done at just the right time,
otherwise some bridge chips (or some Display Driver ICs) may
not work correctly: this is seen at least with a Parade DSI to
eDP bridge (PS8640) on the MT8173 Elm Chromebook.

This resolves a regression that was seen on the aforementioned
machine, which was happening only after a suspend-resume cycle.

Cc: <[email protected]> # 7.1.x
Fixes: 76255024cadb ("drm/mediatek: mtk_dsi: enable hs clock during pre-enable")
Signed-off-by: AngeloGioacchino Del Regno <[email protected]>
Tested-by: Adam Thiede <[email protected]>
Reviewed-by: CK Hu <[email protected]>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/[email protected]/
Signed-off-by: Chun-Kuang Hu <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 drivers/gpu/drm/mediatek/mtk_dsi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
index 2934dc2d841cd..36ac8c1322da8 100644
--- a/drivers/gpu/drm/mediatek/mtk_dsi.c
+++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
@@ -743,8 +743,6 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
 	mtk_dsi_set_vm_cmd(dsi);
 	mtk_dsi_config_vdo_timing(dsi);
 	mtk_dsi_set_interrupt_enable(dsi);
-	mtk_dsi_lane_ready(dsi);
-	mtk_dsi_clk_hs_mode(dsi, 1);
 
 	return 0;
 err_disable_engine_clk:
@@ -858,6 +856,9 @@ static void mtk_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge,
 	ret = mtk_dsi_poweron(dsi);
 	if (ret < 0)
 		drm_err(drm, "failed to power on dsi\n");
+
+	mtk_dsi_lane_ready(dsi);
+	mtk_dsi_clk_hs_mode(dsi, 1);
 }
 
 static void mtk_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge,
-- 
2.53.0