drm/panel: ltk500hd1829: Don't call unprepare+disable at shutdown/remove

It's the responsibility of a correctly written DRM modeset driver to
call drm_atomic_helper_shutdown() at shutdown time and that should be
disabling / unpreparing the panel if needed. Panel drivers shouldn't
be calling these functions themselves.

A recent effort was made to fix as many DRM modeset drivers as
possible [1] [2] [3] and most drivers are fixed now.

Unfortunately, grepping mainline for this panel's compatible string
shows no hits, so we can't be 100% sure if the DRM modeset driver used
with this panel has been fixed. If it is found that the DRM modeset
driver hasn't been fixed then this patch could be temporarily reverted
until it is.

[1] https://lore.kernel.org/r/20230901234015.566018-1-dianders@chromium.org
[2] https://lore.kernel.org/r/20230901234202.566951-1-dianders@chromium.org
[3] https://lore.kernel.org/r/20230921192749.1542462-1-dianders@chromium.orgAcked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503143327.RFT.v2.17.If3edcf846f754b425959980039372a9fd1599ecc@changeid

drivers/gpu/drm/panel/panel-leadtek-ltk500hd1829.c

@@ -662,27 +662,11 @@ static int ltk500hd1829_probe(struct mipi_dsi_device *dsi)
 	return 0;
 }
 
-static void ltk500hd1829_shutdown(struct mipi_dsi_device *dsi)
-{
-	struct ltk500hd1829 *ctx = mipi_dsi_get_drvdata(dsi);
-	int ret;
-
-	ret = drm_panel_unprepare(&ctx->panel);
-	if (ret < 0)
-		dev_err(&dsi->dev, "Failed to unprepare panel: %d\n", ret);
-
-	ret = drm_panel_disable(&ctx->panel);
-	if (ret < 0)
-		dev_err(&dsi->dev, "Failed to disable panel: %d\n", ret);
-}
-
 static void ltk500hd1829_remove(struct mipi_dsi_device *dsi)
 {
 	struct ltk500hd1829 *ctx = mipi_dsi_get_drvdata(dsi);
 	int ret;
 
-	ltk500hd1829_shutdown(dsi);
-
 	ret = mipi_dsi_detach(dsi);
 	if (ret < 0)
 		dev_err(&dsi->dev, "failed to detach from DSI host: %d\n", ret);
@@ -710,7 +694,6 @@ static struct mipi_dsi_driver ltk500hd1829_driver = {
 	},
 	.probe = ltk500hd1829_probe,
 	.remove = ltk500hd1829_remove,
-	.shutdown = ltk500hd1829_shutdown,
 };
 module_mipi_dsi_driver(ltk500hd1829_driver);