Re: [v4 2/4] drm/panel-simple: Support for delays between GPIO & regulator

Hi,

On Tue, May 25, 2021 at 12:31 AM Rajeev Nandan rajeevny@codeaurora.org wrote:

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

Signed-off-by: Rajeev Nandan rajeevny@codeaurora.org

Changes in v4:

• New

drivers/gpu/drm/panel/panel-simple.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c index f9e4e60..caed71b 100644 --- a/drivers/gpu/drm/panel/panel-simple.c +++ b/drivers/gpu/drm/panel/panel-simple.c @@ -134,6 +134,22 @@ 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) that it takes for the panel to
  

•            * turn the display on.
  

Maybe a slightly better description:

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) that it takes for the panel to
  

•            * turn the display off.
  

Maybe a slightly better description:

The time (in milliseconds) to wait after disabling the display before 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
  

@@ -367,6 +383,10 @@ 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);
  

I wonder if it's worth a warning if "p->desc->delay.disable_to_power_off" is non-zero and p->enable_gpio is NULL? I guess in theory it'd also be nice to confirm that p->supply wasn't a dummy regulator, but that's slightly harder.

    regulator_disable(p->supply);
    p->unprepared_time = ktime_get();

@@ -427,6 +447,9 @@ 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);
  

Similar to above: I wonder if it's worth a warning if "p->desc->delay.power_to_enable" is non-zero and p->enable_gpio is NULL?

-Doug