linux-kernel - Re: [PATCH v4 1/2] drm/bridge: dumb-vga-dac: Support a VDD regulator supply

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Date:   Thu, 17 Nov 2016 13:18:58 +0530
From:   Archit Taneja <architt@...eaurora.org>
To:     Chen-Yu Tsai <wens@...e.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        David Airlie <airlied@...ux.ie>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v4 1/2] drm/bridge: dumb-vga-dac: Support a VDD regulator
 supply

Hi,

Thanks for the patch.

On 11/16/2016 09:12 PM, Chen-Yu Tsai wrote:
> Some dumb VGA DACs are active components which require external power.
> Add support for specifying a regulator as its power supply.
>
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> Acked-by: Rob Herring <robh@...nel.org>
> ---
>  .../bindings/display/bridge/dumb-vga-dac.txt       |  2 ++
>  drivers/gpu/drm/bridge/dumb-vga-dac.c              | 35 ++++++++++++++++++++++
>  2 files changed, 37 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> index 003bc246a270..164cbb15f04c 100644
> --- a/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga-dac.txt
> @@ -16,6 +16,8 @@ graph bindings specified in Documentation/devicetree/bindings/graph.txt.
>  - Video port 0 for RGB input
>  - Video port 1 for VGA output
>
> +Optional properties:
> +- vdd-supply: Power supply for DAC
>
>  Example
>  -------
> diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c b/drivers/gpu/drm/bridge/dumb-vga-dac.c
> index afec232185a7..15b549f94307 100644
> --- a/drivers/gpu/drm/bridge/dumb-vga-dac.c
> +++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c
> @@ -12,6 +12,7 @@
>
>  #include <linux/module.h>
>  #include <linux/of_graph.h>
> +#include <linux/regulator/consumer.h>
>
>  #include <drm/drmP.h>
>  #include <drm/drm_atomic_helper.h>
> @@ -23,6 +24,7 @@ struct dumb_vga {
>  	struct drm_connector	connector;
>
>  	struct i2c_adapter	*ddc;
> +	struct regulator	*vdd;
>  };
>
>  static inline struct dumb_vga *
> @@ -124,8 +126,32 @@ static int dumb_vga_attach(struct drm_bridge *bridge)
>  	return 0;
>  }
>
> +static void dumb_vga_enable(struct drm_bridge *bridge)
> +{
> +	struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
> +	int ret = 0;
> +
> +	if (vga->vdd)
> +		ret = regulator_enable(vga->vdd);
> +
> +	if (ret) {
> +		DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
> +		return;

We don't need this return for now. If you're okay with it, can I fix this
and queue to misc?

Thanks,
Archit

> +	}
> +}
> +
> +static void dumb_vga_disable(struct drm_bridge *bridge)
> +{
> +	struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
> +
> +	if (vga->vdd)
> +		regulator_disable(vga->vdd);
> +}
> +
>  static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
>  	.attach		= dumb_vga_attach,
> +	.enable		= dumb_vga_enable,
> +	.disable	= dumb_vga_disable,
>  };
>
>  static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
> @@ -169,6 +195,15 @@ static int dumb_vga_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  	platform_set_drvdata(pdev, vga);
>
> +	vga->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
> +	if (IS_ERR(vga->vdd)) {
> +		ret = PTR_ERR(vga->vdd);
> +		if (ret == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +		vga->vdd = NULL;
> +		dev_dbg(&pdev->dev, "No vdd regulator found: %d\n", ret);
> +	}
> +
>  	vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
>  	if (IS_ERR(vga->ddc)) {
>  		if (PTR_ERR(vga->ddc) == -ENODEV) {
>

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