[PATCH v2 2/5] drm/panel: raydium-rm68200: Fix prepare error cleanup

[Hsieh Hung-En <hungen3108@gmail.com>]

rm68200_prepare() returns without disabling the supply regulator if
EXIT_SLEEP_MODE or SET_DISPLAY_ON fails. Since drm_panel_prepare() does
not mark the panel as prepared on failure, drm_panel_unprepare() does
not call the driver's unprepare() callback, leaving the regulator
enable count elevated even after subsequent successful
prepare/unprepare cycles.

On failure, restore the reset GPIO to its unprepared state, following
the existing reset sequence in unprepare(), and disable the supply
regulator before returning the original error.

Fixes: 2b7ed18bed1a ("drm/panel: Add support for Raydium RM68200 panel driver")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/r/sashiko-outbox-171393@kernel.org
Signed-off-by: Hsieh Hung-En <hungen3108@gmail.com>
---

Notes:
    In this patch, rm68200_init_sequence() still returns void and only
    logs DCS write failures. These failures do not cause prepare() to
    return early. A later patch in this series will propagate
    initialization errors through prepare(), where this cleanup path
    will also handle them.
    
    The error path does not send SET_DISPLAY_OFF or ENTER_SLEEP_MODE,
    as DCS communication may already have failed. Instead, it follows
    the existing reset and regulator shutdown sequence in unprepare().

 drivers/gpu/drm/panel/panel-raydium-rm68200.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-raydium-rm68200.c b/drivers/gpu/drm/panel/panel-raydium-rm68200.c
index c535dc931903..3a59eb00274d 100644
--- a/drivers/gpu/drm/panel/panel-raydium-rm68200.c
+++ b/drivers/gpu/drm/panel/panel-raydium-rm68200.c
@@ -277,17 +277,26 @@ static int rm68200_prepare(struct drm_panel *panel)
 
 	ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
 	if (ret)
-		return ret;
+		goto assert_reset;
 
 	msleep(125);
 
 	ret = mipi_dsi_dcs_set_display_on(dsi);
 	if (ret)
-		return ret;
+		goto assert_reset;
 
 	msleep(20);
 
 	return 0;
+
+assert_reset:
+	if (ctx->reset_gpio) {
+		gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+		msleep(20);
+	}
+	/* Balance the regulator enable count on prepare failure. */
+	regulator_disable(ctx->supply);
+	return ret;
 }
 
 static int rm68200_get_modes(struct drm_panel *panel,
-- 
2.43.0