drm/mediatek: dsi: Move mtk_dsi_stop() call back to mtk_dsi_poweroff()

As the comment right before the mtk_dsi_stop() call advises,
mtk_dsi_stop() should only be called after
mtk_drm_crtc_atomic_disable(). That's because that function calls
drm_crtc_wait_one_vblank(), which requires the vblank irq to be enabled.

Previously mtk_dsi_stop(), being in mtk_dsi_poweroff() and guarded by a
refcount, would only be called at the end of
mtk_drm_crtc_atomic_disable(), through the call to mtk_crtc_ddp_hw_fini().
Commit cde7e2e ("drm/mediatek: Separate poweron/poweroff from
enable/disable and define new funcs") moved the mtk_dsi_stop() call to
mtk_output_dsi_disable(), causing it to be called before
mtk_drm_crtc_atomic_disable(), and consequently generating vblank
timeout warnings during suspend.

Move the mtk_dsi_stop() call back to mtk_dsi_poweroff() so that we have
a working vblank irq during mtk_drm_crtc_atomic_disable() and stop
getting vblank timeout warnings.

Fixes: cde7e2e ("drm/mediatek: Separate poweron/poweroff from enable/disable and define new funcs")
Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Link: http://lists.infradead.org/pipermail/linux-mediatek/2022-August/046713.html
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

Author: nfraprado

drivers/gpu/drm/mediatek/mtk_dsi.c

@@ -685,6 +685,16 @@ static void mtk_dsi_poweroff(struct mtk_dsi *dsi)
 	if (--dsi->refcount != 0)
 		return;
 
+	/*
+	 * mtk_dsi_stop() and mtk_dsi_start() is asymmetric, since
+	 * mtk_dsi_stop() should be called after mtk_drm_crtc_atomic_disable(),
+	 * which needs irq for vblank, and mtk_dsi_stop() will disable irq.
+	 * mtk_dsi_start() needs to be called in mtk_output_dsi_enable(),
+	 * after dsi is fully set.
+	 */
+	mtk_dsi_stop(dsi);
+
+	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
 	mtk_dsi_reset_engine(dsi);
 	mtk_dsi_lane0_ulp_mode_enter(dsi);
 	mtk_dsi_clk_ulp_mode_enter(dsi);
@@ -735,17 +745,6 @@ static void mtk_output_dsi_disable(struct mtk_dsi *dsi)
 	if (!dsi->enabled)
 		return;
 
-	/*
-	 * mtk_dsi_stop() and mtk_dsi_start() is asymmetric, since
-	 * mtk_dsi_stop() should be called after mtk_drm_crtc_atomic_disable(),
-	 * which needs irq for vblank, and mtk_dsi_stop() will disable irq.
-	 * mtk_dsi_start() needs to be called in mtk_output_dsi_enable(),
-	 * after dsi is fully set.
-	 */
-	mtk_dsi_stop(dsi);
-
-	mtk_dsi_switch_to_cmd_mode(dsi, VM_DONE_INT_FLAG, 500);
-
 	dsi->enabled = false;
 }