[PATCH 2/4] drm/tegra: dsi: Clear enable register if powered by bootloader

[Diogo Ivo]

In cases where the DSI module is left on by the bootloader
some panels may fail to initialize if the enable register is not cleared
before the panel's initialization sequence. Clear it and add an optional
device tree property to inform the driver if this is the case.

Signed-off-by: Diogo Ivo <diogo.ivo at tecnico.ulisboa.pt>
---
 drivers/gpu/drm/tegra/dsi.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
index de1333dc0d86..f66514379913 100644
--- a/drivers/gpu/drm/tegra/dsi.c
+++ b/drivers/gpu/drm/tegra/dsi.c
@@ -78,6 +78,8 @@ struct tegra_dsi {
 	unsigned int video_fifo_depth;
 	unsigned int host_fifo_depth;
 
+	bool enabled;
+
 	/* for ganged-mode support */
 	struct tegra_dsi *master;
 	struct tegra_dsi *slave;
@@ -460,6 +462,8 @@ static void tegra_dsi_enable(struct tegra_dsi *dsi)
 	value |= DSI_POWER_CONTROL_ENABLE;
 	tegra_dsi_writel(dsi, value, DSI_POWER_CONTROL);
 
+	dsi->enabled = true;
+
 	if (dsi->slave)
 		tegra_dsi_enable(dsi->slave);
 }
@@ -737,6 +741,8 @@ static void tegra_dsi_disable(struct tegra_dsi *dsi)
 	value &= ~DSI_POWER_CONTROL_ENABLE;
 	tegra_dsi_writel(dsi, value, DSI_POWER_CONTROL);
 
+	dsi->enabled = false;
+
 	if (dsi->slave)
 		tegra_dsi_disable(dsi->slave);
 
@@ -912,6 +918,27 @@ static void tegra_dsi_encoder_enable(struct drm_encoder *encoder)
 	u32 value;
 	int err;
 
+	/* If the bootloader enabled DSI it needs to be disabled
+	 * in order for the panel initialization commands to be
+	 * properly sent.
+	 */
+	if (dsi->enabled) {
+		if (dc) {
+			value = tegra_dc_readl(dc, DC_DISP_DISP_WIN_OPTIONS);
+			value &= ~DSI_ENABLE;
+			tegra_dc_writel(dc, value, DC_DISP_DISP_WIN_OPTIONS);
+
+			tegra_dc_commit(dc);
+		}
+
+		err = tegra_dsi_wait_idle(dsi, 100);
+		if (err < 0)
+			dev_dbg(dsi->dev, "failed to idle DSI: %d\n", err);
+
+		/* disable DSI controller */
+		tegra_dsi_disable(dsi);
+	}
+
 	err = tegra_dsi_prepare(dsi);
 	if (err < 0) {
 		dev_err(dsi->dev, "failed to prepare: %d\n", err);
@@ -1573,6 +1600,8 @@ static int tegra_dsi_probe(struct platform_device *pdev)
 
 	dsi->output.connector.polled = DRM_CONNECTOR_POLL_HPD;
 
+	/* Check if the DSI module was left on by bootloader. */
+	dsi->enabled = of_property_read_bool(pdev->dev.of_node, "nvidia,boot-on");
 	/*
 	 * Assume these values by default. When a DSI peripheral driver
 	 * attaches to the DSI host, the parameters will be taken from
-- 
2.37.3