Revert "drm/panel-simple: Support for delays between GPIO & regulator"

This reverts commit 18a1488b.

Those delays were added to support the Samsung ATNA33XC20
panel. However, we've moving that to its own panel driver and out of
panel-simple. That means we don't need the ability to specify this
delay.

NOTE: it's unlikely we want to keep this delay "just in case" some
other panel needs it. The enable-gpio and the power supply are really
supposed to be different ways to specify the same thing: the main
enable of the panel. Supporting a delay between them doesn't really
make sense.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210730084534.v2.5.Ie44e3e5b7a926392541d575ca84c56931596513f@changeid

drivers/gpu/drm/panel/panel-simple.c

@@ -132,22 +132,6 @@ struct panel_desc {
 		 */
 		unsigned int prepare_to_enable;
 
-		/**
-		 * @delay.power_to_enable: Time for the power to enable the display on.
-		 *
-		 * The time (in milliseconds) to wait after powering up the display
-		 * before asserting its enable pin.
-		 */
-		unsigned int power_to_enable;
-
-		/**
-		 * @delay.disable_to_power_off: Time for the disable to power the display off.
-		 *
-		 * The time (in milliseconds) to wait before powering off the display
-		 * after deasserting its enable pin.
-		 */
-		unsigned int disable_to_power_off;
-
 		/**
 		 * @delay.enable: Time for the panel to display a valid frame.
 		 *
@@ -363,10 +347,6 @@ static int panel_simple_suspend(struct device *dev)
 	struct panel_simple *p = dev_get_drvdata(dev);
 
 	gpiod_set_value_cansleep(p->enable_gpio, 0);
-
-	if (p->desc->delay.disable_to_power_off)
-		msleep(p->desc->delay.disable_to_power_off);
-
 	regulator_disable(p->supply);
 	p->unprepared_time = ktime_get();
 
@@ -427,9 +407,6 @@ static int panel_simple_prepare_once(struct panel_simple *p)
 		return err;
 	}
 
-	if (p->desc->delay.power_to_enable)
-		msleep(p->desc->delay.power_to_enable);
-
 	gpiod_set_value_cansleep(p->enable_gpio, 1);
 
 	delay = p->desc->delay.prepare;
@@ -803,11 +780,6 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc,
 		break;
 	}
 
-	if (!panel->enable_gpio && desc->delay.disable_to_power_off)
-		dev_warn(dev, "Need a delay after disabling panel GPIO, but a GPIO wasn't provided\n");
-	if (!panel->enable_gpio && desc->delay.power_to_enable)
-		dev_warn(dev, "Need a delay before enabling panel GPIO, but a GPIO wasn't provided\n");
-
 	dev_set_drvdata(dev, panel);
 
 	/*