Re: [v5 3/5] drm/panel-simple: Support for delays between GPIO & regulator

Some panels datasheets may specify a delay between the enable GPIO and
the regulator. Support this in panel-simple.

Signed-off-by: Rajeev Nandan <redacted>
---

Changes in v4:
- New

Changes in v5:
- Update description (Douglas)
- Warn if "power_to_enable" or "disable_to_power_off" is non-zero and panel->enable_gpio
  is NULL (Douglas)

 drivers/gpu/drm/panel/panel-simple.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 047fad5..e3f5b7e 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c

@@ -133,6 +133,22 @@ 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.
                 *
                 * The time (in milliseconds) that it takes for the panel to

@@ -347,6 +363,10 @@ 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();

@@ -407,6 +427,9 @@ 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;

@@ -782,6 +805,11 @@ 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, "Specify enable_gpio when using disable_to_power_off delay\n");
+       if (!panel->enable_gpio && desc->delay.power_to_enable)
+               dev_warn(dev, "Specify enable_gpio when using power_to_enable delay\n");