[PATCH] drm/tilcdc: do the complete reset sequence if the LCDC is enabled

[Emiliano Ingrassia]

If the LCD controller was already enabled (e.g. by the bootloader),
do the complete software reset sequence to avoid time out while loading
the palette and a consequent time out waiting for vblank.

Signed-off-by: Emiliano Ingrassia <ingrassia at epigenesys.com>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 3621ff42979f..589156b2f76c 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -208,10 +208,33 @@ static void reset(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
 	struct tilcdc_drm_private *priv = dev->dev_private;
+	struct tilcdc_crtc *tilcdc_crtc = to_tilcdc_crtc(crtc);
+	int ret;
 
 	if (priv->rev != 2)
 		return;
 
+	/*
+	 * If the LCDC was already enabled (e.g. by the bootloader)
+	 * do the complete software reset sequence.
+	 */
+	if (tilcdc_read(dev, LCDC_RASTER_CTRL_REG) & LCDC_RASTER_ENABLE) {
+
+		/* Enable DMA Frame Done Interrupt */
+		tilcdc_write(dev, LCDC_INT_ENABLE_SET_REG, LCDC_FRAME_DONE);
+		tilcdc_clear_irqstatus(dev, 0xffffffff);
+
+		tilcdc_crtc->frame_done = false;
+		tilcdc_clear(dev, LCDC_RASTER_CTRL_REG, LCDC_RASTER_ENABLE);
+
+		ret = wait_event_timeout(tilcdc_crtc->frame_done_wq,
+					 tilcdc_crtc->frame_done,
+					 msecs_to_jiffies(500));
+		if (ret == 0)
+			dev_err(dev->dev, "%s: timeout waiting for framedone while resetting LCDC\n",
+				__func__);
+	}
+
 	tilcdc_set(dev, LCDC_CLK_RESET_REG, LCDC_CLK_MAIN_RESET);
 	usleep_range(250, 1000);
 	tilcdc_clear(dev, LCDC_CLK_RESET_REG, LCDC_CLK_MAIN_RESET);
-- 
2.11.0