drm/tegra: dsi - Add enable guard

To prevent the enable or disable operations to potentially be run
multiple times, add guards to return early when the output is already
in the targetted state.
Signed-off-by: NThierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/dsi.c

@@ -53,6 +53,7 @@ struct tegra_dsi {
 	struct mipi_dsi_host host;
 
 	struct regulator *vdd;
+	bool enabled;
 };
 
 static inline struct tegra_dsi *
@@ -436,6 +437,9 @@ static int tegra_output_dsi_enable(struct tegra_output *output)
 	const u32 *pkt_seq;
 	int err;
 
+	if (dsi->enabled)
+		return 0;
+
 	if (dsi->flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) {
 		DRM_DEBUG_KMS("Non-burst video mode with sync pulses\n");
 		pkt_seq = pkt_seq_video_non_burst_sync_pulses;
@@ -530,6 +534,8 @@ static int tegra_output_dsi_enable(struct tegra_output *output)
 	value |= DSI_POWER_CONTROL_ENABLE;
 	tegra_dsi_writel(dsi, value, DSI_POWER_CONTROL);
 
+	dsi->enabled = true;
+
 	return 0;
 }
 
@@ -539,6 +545,9 @@ static int tegra_output_dsi_disable(struct tegra_output *output)
 	struct tegra_dsi *dsi = to_dsi(output);
 	unsigned long value;
 
+	if (!dsi->enabled)
+		return 0;
+
 	/* disable DSI controller */
 	value = tegra_dsi_readl(dsi, DSI_POWER_CONTROL);
 	value &= DSI_POWER_CONTROL_ENABLE;
@@ -568,6 +577,8 @@ static int tegra_output_dsi_disable(struct tegra_output *output)
 
 	clk_disable(dsi->clk);
 
+	dsi->enabled = false;
+
 	return 0;
 }