Messages in this thread |  | | Date | Mon, 16 Dec 2019 14:06:15 +0100 | From | Maxime Ripard <> | Subject | Re: [PATCH] drm/panel: simple: Support reset GPIOs |
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Hi,
On Fri, Dec 13, 2019 at 07:13:25PM +0100, Miquel Raynal wrote: > The panel common bindings provide a gpios-reset property which is > active low by default. Let's support it in the simple driver. > > De-asserting the reset pin implies a physical high, which in turns is > a logic low. > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
The GPIOd API asks for a logical state, so it doesn't really matter what the polarity of the GPIO, OUT_LOW will always mean that the reset is deasserted (and thus, it will work even if the reset pin is active high).
> --- > drivers/gpu/drm/panel/panel-simple.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c > index 5d487686d25c..15dd495c347d 100644 > --- a/drivers/gpu/drm/panel/panel-simple.c > +++ b/drivers/gpu/drm/panel/panel-simple.c > @@ -110,6 +110,7 @@ struct panel_simple { > struct i2c_adapter *ddc; > > struct gpio_desc *enable_gpio; > + struct gpio_desc *reset_gpio; > > struct drm_display_mode override_mode; > }; > @@ -433,12 +434,21 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc) > if (IS_ERR(panel->supply)) > return PTR_ERR(panel->supply); > > + panel->reset_gpio = devm_gpiod_get_optional(dev, "reset", > + GPIOD_OUT_LOW); > + if (IS_ERR(panel->reset_gpio)) { > + err = PTR_ERR(panel->reset_gpio); > + if (err != -EPROBE_DEFER) > + dev_err(dev, "failed to request reset pin: %d\n", err); > + return err; > + } > +
However, I'm wondering if it wouldn't be better to just have the device maintained in reset at probe (so OUT_HIGH) and moved out of reset during either the prepare or enable callbacks.
This is pretty much what is happening with the enable-gpios already.
Also, panels usually need to wait for a minimum time after you deassert the reset line. How is that dealt with?
I guess a good way to do that would be to add that duration to the panel description, since this is pretty much device specific.
Thanks! Maxime [unhandled content-type:application/pgp-signature] |  |