drm/panel: otm8009a: Don't double check prepared/enabled

As talked about in commit d2aacaf ("drm/panel: Check for already
prepared/enabled in drm_panel"), we want to remove needless code from
panel drivers that was storing and double-checking the
prepared/enabled state. Even if someone was relying on the
double-check before, that double-check is now in the core and not
needed in individual drivers.

For the "otm8009a" driver we fully remove the storing of the "enabled"
state and we remove the double-checking, but we still keep the storing
of the "prepared" state since the backlight code in the driver checks
it. This backlight code may not be perfectly safe since there doesn't
appear to be sufficient synchronization between the backlight driver
(which userspace can call into directly) and the code that's
unpreparing the panel. However, this lack of safety is not new and can
be addressed in a future patch.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230804140605.RFC.3.I6a4a3c81c78acf5acdc2e5b5d936e19bf57ec07a@changeid

drivers/gpu/drm/panel/panel-orisetech-otm8009a.c

@@ -70,7 +70,6 @@ struct otm8009a {
 	struct gpio_desc *reset_gpio;
 	struct regulator *supply;
 	bool prepared;
-	bool enabled;
 };
 
 static const struct drm_display_mode modes[] = {
@@ -267,9 +266,6 @@ static int otm8009a_disable(struct drm_panel *panel)
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
 	int ret;
 
-	if (!ctx->enabled)
-		return 0; /* This is not an issue so we return 0 here */
-
 	backlight_disable(ctx->bl_dev);
 
 	ret = mipi_dsi_dcs_set_display_off(dsi);
@@ -282,18 +278,13 @@ static int otm8009a_disable(struct drm_panel *panel)
 
 	msleep(120);
 
-	ctx->enabled = false;
-
 	return 0;
 }
 
 static int otm8009a_unprepare(struct drm_panel *panel)
 {
 	struct otm8009a *ctx = panel_to_otm8009a(panel);
 
-	if (!ctx->prepared)
-		return 0;
-
 	if (ctx->reset_gpio) {
 		gpiod_set_value_cansleep(ctx->reset_gpio, 1);
 		msleep(20);
@@ -311,9 +302,6 @@ static int otm8009a_prepare(struct drm_panel *panel)
 	struct otm8009a *ctx = panel_to_otm8009a(panel);
 	int ret;
 
-	if (ctx->prepared)
-		return 0;
-
 	ret = regulator_enable(ctx->supply);
 	if (ret < 0) {
 		dev_err(panel->dev, "failed to enable supply: %d\n", ret);
@@ -341,13 +329,8 @@ static int otm8009a_enable(struct drm_panel *panel)
 {
 	struct otm8009a *ctx = panel_to_otm8009a(panel);
 
-	if (ctx->enabled)
-		return 0;
-
 	backlight_enable(ctx->bl_dev);
 
-	ctx->enabled = true;
-
 	return 0;
 }