drm/panel-simple: Non-eDP panels don't need "HPD" handling

All of the "HPD" handling added to panel-simple recently was for eDP
panels. Remove it from panel-simple now that panel-edp handles eDP
panels. The "prepare_to_enable" delay only makes sense in the context
of HPD, so remove it too. No non-eDP panels used it anyway.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914132020.v5.9.I77d7a48df0a6585ef2cc2ff140fbe8f236a9a9f7@changeid

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

@@ -23,7 +23,6 @@
 
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
-#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
@@ -92,44 +91,6 @@ struct panel_desc {
 		 */
 		unsigned int prepare;
 
-		/**
-		 * @delay.hpd_absent_delay: Time to wait if HPD isn't hooked up.
-		 *
-		 * Add this to the prepare delay if we know Hot Plug Detect
-		 * isn't used.
-		 */
-		unsigned int hpd_absent_delay;
-
-		/**
-		 * @delay.prepare_to_enable: Time between prepare and enable.
-		 *
-		 * The minimum time, in milliseconds, that needs to have passed
-		 * between when prepare finished and enable may begin. If at
-		 * enable time less time has passed since prepare finished,
-		 * the driver waits for the remaining time.
-		 *
-		 * If a fixed enable delay is also specified, we'll start
-		 * counting before delaying for the fixed delay.
-		 *
-		 * If a fixed prepare delay is also specified, we won't start
-		 * counting until after the fixed delay. We can't overlap this
-		 * fixed delay with the min time because the fixed delay
-		 * doesn't happen at the end of the function if a HPD GPIO was
-		 * specified.
-		 *
-		 * In other words:
-		 *   prepare()
-		 *     ...
-		 *     // do fixed prepare delay
-		 *     // wait for HPD GPIO if applicable
-		 *     // start counting for prepare_to_enable
-		 *
-		 *   enable()
-		 *     // do fixed enable delay
-		 *     // enforce prepare_to_enable min time
-		 */
-		unsigned int prepare_to_enable;
-
 		/**
 		 * @delay.enable: Time for the panel to display a valid frame.
 		 *
@@ -174,7 +135,6 @@ struct panel_desc {
 struct panel_simple {
 	struct drm_panel base;
 	bool enabled;
-	bool no_hpd;
 
 	bool prepared;
 
@@ -187,7 +147,6 @@ struct panel_simple {
 	struct i2c_adapter *ddc;
 
 	struct gpio_desc *enable_gpio;
-	struct gpio_desc *hpd_gpio;
 
 	struct edid *edid;
 
@@ -371,31 +330,11 @@ static int panel_simple_unprepare(struct drm_panel *panel)
 	return 0;
 }
 
-static int panel_simple_get_hpd_gpio(struct device *dev, struct panel_simple *p)
+static int panel_simple_resume(struct device *dev)
 {
+	struct panel_simple *p = dev_get_drvdata(dev);
 	int err;
 
-	p->hpd_gpio = devm_gpiod_get_optional(dev, "hpd", GPIOD_IN);
-	if (IS_ERR(p->hpd_gpio)) {
-		err = PTR_ERR(p->hpd_gpio);
-
-		if (err != -EPROBE_DEFER)
-			dev_err(dev, "failed to get 'hpd' GPIO: %d\n", err);
-
-		return err;
-	}
-
-	return 0;
-}
-
-static int panel_simple_prepare_once(struct panel_simple *p)
-{
-	struct device *dev = p->base.dev;
-	unsigned int delay;
-	int err;
-	int hpd_asserted;
-	unsigned long hpd_wait_us;
-
 	panel_simple_wait(p->unprepared_time, p->desc->delay.unprepare);
 
 	err = regulator_enable(p->supply);
@@ -406,68 +345,12 @@ static int panel_simple_prepare_once(struct panel_simple *p)
 
 	gpiod_set_value_cansleep(p->enable_gpio, 1);
 
-	delay = p->desc->delay.prepare;
+	if (p->desc->delay.prepare)
-	if (p->no_hpd)
+		msleep(p->desc->delay.prepare);
-		delay += p->desc->delay.hpd_absent_delay;
-	if (delay)
-		msleep(delay);
-
-	if (p->hpd_gpio) {
-		if (p->desc->delay.hpd_absent_delay)
-			hpd_wait_us = p->desc->delay.hpd_absent_delay * 1000UL;
-		else
-			hpd_wait_us = 2000000;
-
-		err = readx_poll_timeout(gpiod_get_value_cansleep, p->hpd_gpio,
-					 hpd_asserted, hpd_asserted,
-					 1000, hpd_wait_us);
-		if (hpd_asserted < 0)
-			err = hpd_asserted;
-
-		if (err) {
-			if (err != -ETIMEDOUT)
-				dev_err(dev,
-					"error waiting for hpd GPIO: %d\n", err);
-			goto error;
-		}
-	}
 
 	p->prepared_time = ktime_get();
 
 	return 0;
-
-error:
-	gpiod_set_value_cansleep(p->enable_gpio, 0);
-	regulator_disable(p->supply);
-	p->unprepared_time = ktime_get();
-
-	return err;
-}
-
-/*
- * Some panels simply don't always come up and need to be power cycled to
- * work properly.  We'll allow for a handful of retries.
- */
-#define MAX_PANEL_PREPARE_TRIES		5
-
-static int panel_simple_resume(struct device *dev)
-{
-	struct panel_simple *p = dev_get_drvdata(dev);
-	int ret;
-	int try;
-
-	for (try = 0; try < MAX_PANEL_PREPARE_TRIES; try++) {
-		ret = panel_simple_prepare_once(p);
-		if (ret != -ETIMEDOUT)
-			break;
-	}
-
-	if (ret == -ETIMEDOUT)
-		dev_err(dev, "Prepare timeout after %d tries\n", try);
-	else if (try)
-		dev_warn(dev, "Prepare needed %d retries\n", try);
-
-	return ret;
 }
 
 static int panel_simple_prepare(struct drm_panel *panel)
@@ -500,8 +383,6 @@ static int panel_simple_enable(struct drm_panel *panel)
 	if (p->desc->delay.enable)
 		msleep(p->desc->delay.enable);
 
-	panel_simple_wait(p->prepared_time, p->desc->delay.prepare_to_enable);
-
 	p->enabled = true;
 
 	return 0;
@@ -674,13 +555,6 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	panel->prepared_time = 0;
 	panel->desc = desc;
 
-	panel->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
-	if (!panel->no_hpd) {
-		err = panel_simple_get_hpd_gpio(dev, panel);
-		if (err)
-			return err;
-	}
-
 	panel->supply = devm_regulator_get(dev, "power");
 	if (IS_ERR(panel->supply))
 		return PTR_ERR(panel->supply);