[PATCH 2/4] drm/panel: st7703: move init commands to prepare()

[Marc-Olivier Champagne]

The panel init sequence is currently sent from enable(), i.e. after
the DSI host has started the video stream. Not all DSI hosts accept
command packets in that state, so the init sequence may never reach
the panel.

Move the init sequence to prepare(), right after the panel reset, to
ensure it is sent before the host enables the video stream.

Since the init sequence can now fail in prepare(), power the panel
back down on error: the panel core does not call unprepare() when
prepare() fails, leaving the power supplies enabled.

Both patterns are already used by other DSI panel drivers.

Suggested-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
Signed-off-by: Marc-Olivier Champagne <marc-olivier.champagne@xxxxxxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/panel/panel-sitronix-st7703.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
index 368c57591817..f4635a7327de 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
@@ -774,8 +774,6 @@ static int st7703_enable(struct drm_panel *panel)
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
 	struct mipi_dsi_multi_context dsi_ctx = {.dsi = dsi};
 
-	ctx->desc->init_sequence(&dsi_ctx);
-
 	mipi_dsi_dcs_exit_sleep_mode_multi(&dsi_ctx);
 
 	/* It takes the controller 120 msec to wake up after sleep. */
@@ -784,7 +782,7 @@ static int st7703_enable(struct drm_panel *panel)
 	mipi_dsi_dcs_set_display_on_multi(&dsi_ctx);
 
 	if (!dsi_ctx.accum_err)
-		dev_dbg(ctx->dev, "Panel init sequence done\n");
+		dev_dbg(ctx->dev, "Panel enable done\n");
 
 	return dsi_ctx.accum_err;
 }
@@ -819,6 +817,8 @@ static int st7703_unprepare(struct drm_panel *panel)
 static int st7703_prepare(struct drm_panel *panel)
 {
 	struct st7703 *ctx = panel_to_st7703(panel);
+	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
+	struct mipi_dsi_multi_context dsi_ctx = {.dsi = dsi};
 	int ret;
 
 	dev_dbg(ctx->dev, "Resetting the panel\n");
@@ -843,6 +843,18 @@ static int st7703_prepare(struct drm_panel *panel)
 	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
 	usleep_range(15000, 20000);
 
+	ctx->desc->init_sequence(&dsi_ctx);
+
+	if (dsi_ctx.accum_err) {
+		gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+		regulator_disable(ctx->iovcc);
+		regulator_disable(ctx->vcc);
+
+		return dsi_ctx.accum_err;
+	}
+
+	dev_dbg(ctx->dev, "Panel init sequence done\n");
+
 	return 0;
 }
 
-- 
2.34.1