drm/mcde: Fix frame sync setup for video mode panels

The MCDE driver differentiates only between "te_sync"
(for hardware TE0 sync) and software sync
(i.e. manually triggered updates) at the moment.

However, none of these options work correctly for video mode panels.
Therefore, we need to make some changes to make them work correctly:

  - Select hardware sync coming from the (DSI) formatter.
  - Keep the FIFO permanently enabled (otherwise MCDE will stop
    feeding data to the panel).
  - Skip manual software sync (this is not necessary in video mode).

Automatically detect if the connected panel is using video mode
and enable the necessary changes in that case.
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191106165835.2863-3-stephan@gerhold.net

drivers/gpu/drm/mcde/mcde_display.c

@@ -498,24 +498,20 @@ static void mcde_configure_channel(struct mcde *mcde, enum mcde_channel ch,
 	}
 
 	/* Set up channel 0 sync (based on chnl_update_registers()) */
-	if (mcde->te_sync) {
-		/*
-		 * Turn on hardware TE0 synchronization
-		 */
+	if (mcde->video_mode || mcde->te_sync)
 		val = MCDE_CHNLXSYNCHMOD_SRC_SYNCH_HARDWARE
 			<< MCDE_CHNLXSYNCHMOD_SRC_SYNCH_SHIFT;
-		val |= MCDE_CHNLXSYNCHMOD_OUT_SYNCH_SRC_TE0
-			<< MCDE_CHNLXSYNCHMOD_OUT_SYNCH_SRC_SHIFT;
-	} else {
-		/*
-		 * Set up sync source to software, out sync formatter
-		 * Code mostly from mcde_hw.c chnl_update_registers()
-		 */
+	else
 		val = MCDE_CHNLXSYNCHMOD_SRC_SYNCH_SOFTWARE
 			<< MCDE_CHNLXSYNCHMOD_SRC_SYNCH_SHIFT;
+
+	if (mcde->te_sync)
+		val |= MCDE_CHNLXSYNCHMOD_OUT_SYNCH_SRC_TE0
+			<< MCDE_CHNLXSYNCHMOD_OUT_SYNCH_SRC_SHIFT;
+	else
 		val |= MCDE_CHNLXSYNCHMOD_OUT_SYNCH_SRC_FORMATTER
 			<< MCDE_CHNLXSYNCHMOD_OUT_SYNCH_SRC_SHIFT;
-	}
+
 	writel(val, mcde->regs + sync);
 
 	/* Set up pixels per line and lines per frame */
@@ -938,6 +934,13 @@ static void mcde_display_enable(struct drm_simple_display_pipe *pipe,
 
 	drm_crtc_vblank_on(crtc);
 
+	if (mcde->video_mode)
+		/*
+		 * Keep FIFO permanently enabled in video mode,
+		 * otherwise MCDE will stop feeding data to the panel.
+		 */
+		mcde_enable_fifo(mcde, MCDE_FIFO_A);
+
 	dev_info(drm->dev, "MCDE display is enabled\n");
 }
 
@@ -1047,8 +1050,9 @@ static void mcde_display_update(struct drm_simple_display_pipe *pipe,
 	 */
 	if (fb) {
 		mcde_set_extsrc(mcde, drm_fb_cma_get_gem_addr(fb, pstate, 0));
-		/* Send a single frame using software sync */
-		mcde_display_send_one_frame(mcde);
+		if (!mcde->video_mode)
+			/* Send a single frame using software sync */
+			mcde_display_send_one_frame(mcde);
 		dev_info_once(mcde->dev, "sent first display update\n");
 	} else {
 		/*

drivers/gpu/drm/mcde/mcde_drm.h

@@ -19,6 +19,7 @@ struct mcde {
 	struct mipi_dsi_device *mdsi;
 	s16 stride;
 	bool te_sync;
+	bool video_mode;
 	bool oneshot_mode;
 	unsigned int flow_active;
 	spinlock_t flow_lock; /* Locks the channel flow control */

drivers/gpu/drm/mcde/mcde_drv.c

@@ -331,8 +331,6 @@ static int mcde_probe(struct platform_device *pdev)
 	drm->dev_private = mcde;
 	platform_set_drvdata(pdev, drm);
 
-	/* Enable use of the TE signal and interrupt */
-	mcde->te_sync = true;
 	/* Enable continuous updates: this is what Linux' framebuffer expects */
 	mcde->oneshot_mode = false;
 	drm->dev_private = mcde;

drivers/gpu/drm/mcde/mcde_dsi.c

@@ -130,6 +130,15 @@ bool mcde_dsi_irq(struct mipi_dsi_device *mdsi)
 	return te_received;
 }
 
+static void mcde_dsi_attach_to_mcde(struct mcde_dsi *d)
+{
+	d->mcde->mdsi = d->mdsi;
+
+	d->mcde->video_mode = !!(d->mdsi->mode_flags & MIPI_DSI_MODE_VIDEO);
+	/* Enable use of the TE signal for all command mode panels */
+	d->mcde->te_sync = !d->mcde->video_mode;
+}
+
 static int mcde_dsi_host_attach(struct mipi_dsi_host *host,
 				struct mipi_dsi_device *mdsi)
 {
@@ -148,7 +157,7 @@ static int mcde_dsi_host_attach(struct mipi_dsi_host *host,
 
 	d->mdsi = mdsi;
 	if (d->mcde)
-		d->mcde->mdsi = mdsi;
+		mcde_dsi_attach_to_mcde(d);
 
 	return 0;
 }
@@ -901,7 +910,7 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
 	d->mcde = mcde;
 	/* If the display attached before binding, set this up */
 	if (d->mdsi)
-		d->mcde->mdsi = d->mdsi;
+		mcde_dsi_attach_to_mcde(d);
 
 	/* Obtain the clocks */
 	d->hs_clk = devm_clk_get(dev, "hs");