[PATCH v2 2/4] drm/tegra: dsi: Clear enable register if powered by bootloader

[Diogo Ivo <diogo.ivo@tecnico.ulisboa.pt>]

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 is sent, so clear it if that
is the case. 

Signed-off-by: Diogo Ivo <diogo.ivo@tecnico.ulisboa.pt>
---
Changes in v2:
 - detect if the DSI module is on based on the register value,
   instead of a DT property.
 - remove Display Controller clear, since it is redundant.

 drivers/gpu/drm/tegra/dsi.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
index de1333dc0d86..5954676a7ab1 100644
--- a/drivers/gpu/drm/tegra/dsi.c
+++ b/drivers/gpu/drm/tegra/dsi.c
@@ -912,6 +912,15 @@ 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.
+	 */
+	value = tegra_dsi_readl(dsi, DSI_POWER_CONTROL);
+
+	if (value & DSI_POWER_CONTROL_ENABLE)
+		tegra_dsi_disable(dsi);
+
 	err = tegra_dsi_prepare(dsi);
 	if (err < 0) {
 		dev_err(dsi->dev, "failed to prepare: %d\n", err);
-- 
2.38.1