drm/panel-edp: Use ktime_get_boottime for delays

ktime_get is based on CLOCK_MONOTONIC which stops on suspend. On
suspend, the time that the panel was powerd off is recorded with
ktime_get, and on resume this time is compared to the current ktime_get
time to determine if the driver should wait for the panel to power down
completely before re-enabling it.

Because we're using ktime_get, this delay doesn't account for the time
that the device is suspended, during which the power down delay may have
already elapsed.

Change to use ktime_get_boottime throughout, which uses CLOCK_BOOTTIME
which does not stop when suspended. This ensures that the resume path
will not be delayed if the power off delay has already been met while
the device is suspended.
Signed-off-by: Drew Davenport <ddavenport@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221117133655.1.I51639dc112bbbe27259df6bdad56dbabd655d91a@changeid

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

@@ -351,7 +351,7 @@ static void panel_edp_wait(ktime_t start_ktime, unsigned int min_ms)
 		return;
 
 	min_ktime = ktime_add(start_ktime, ms_to_ktime(min_ms));
-	now_ktime = ktime_get();
+	now_ktime = ktime_get_boottime();
 
 	if (ktime_before(now_ktime, min_ktime))
 		msleep(ktime_to_ms(ktime_sub(min_ktime, now_ktime)) + 1);
@@ -378,7 +378,7 @@ static int panel_edp_suspend(struct device *dev)
 
 	gpiod_set_value_cansleep(p->enable_gpio, 0);
 	regulator_disable(p->supply);
-	p->unprepared_time = ktime_get();
+	p->unprepared_time = ktime_get_boottime();
 
 	return 0;
 }
@@ -464,14 +464,14 @@ static int panel_edp_prepare_once(struct panel_edp *p)
 		}
 	}
 
-	p->prepared_time = ktime_get();
+	p->prepared_time = ktime_get_boottime();
 
 	return 0;
 
 error:
 	gpiod_set_value_cansleep(p->enable_gpio, 0);
 	regulator_disable(p->supply);
-	p->unprepared_time = ktime_get();
+	p->unprepared_time = ktime_get_boottime();
 
 	return err;
 }