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

Hi,

On Sun, May 30, 2021 at 8:57 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

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");
  

Last nit is that the warning messages could be a little confusing to someone reading the logs. I guess the target audience of the error message is probably someone doing bringup. That person specified a panel in their device tree and maybe isn't even aware that they're using "disable_to_power_off" or "power_to_enable". Maybe wording instead:

Need a delay after disabling panel GPIO, but a GPIO wasn't provided. Need a delay after enabling panel GPIO, but a GPIO wasn't provided.

That's definitely getting into nittiness, though and I wouldn't be upset if the patch landed with the existing messages. Thus, with or without the change to the error message:

Reviewed-by: Douglas Anderson dianders@chromium.org