linux-kernel - Re: [linux-sunxi] Re: [PATCH v3 1/2] drm/bridge: dumb-vga-dac: Support a VDD regulator supply

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Message-ID: <CAGb2v64tTacSAG1vvO28h8MN9JC9w+OzSrP+j2eTzqAiQKgaSA@mail.gmail.com>
Date:   Wed, 2 Nov 2016 09:33:01 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        David Airlie <airlied@...ux.ie>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] Re: [PATCH v3 1/2] drm/bridge: dumb-vga-dac:
 Support a VDD regulator supply

On Mon, Oct 31, 2016 at 2:28 PM, Rob Herring <robh@...nel.org> wrote:
> On Sat, Oct 29, 2016 at 07:06:10PM +0800, 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>
>> ---
>>  .../bindings/display/bridge/dumb-vga-dac.txt       |  2 ++
>
> For the binding,
>
> Acked-by: Rob Herring <robh@...nel.org>
>
> One code comment below...
>
>>  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..59781e031220 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 +126,33 @@ 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;
>> +
>> +     if (!IS_ERR(vga->vdd)) {
>
> if (IS_ERR())
>         return;
>
> ...will save some intentation.

I thought about that, though if someone were to add more stuff to
this, such as an enable GPIO, they might have to rework it. A standalone
block of code would be easier to work with. I'm OK either way though.

ChenYu

>
>> +             ret = regulator_enable(vga->vdd);
>> +
>> +             if (ret) {
>> +                     DRM_ERROR("Failed to enable vdd regulator: %d\n", ret);
>> +                     return;
>> +             }
>> +     }
>> +}
>> +
>> +static void dumb_vga_disable(struct drm_bridge *bridge)
>> +{
>> +     struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
>> +
>> +     if (!IS_ERR(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 +196,14 @@ 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;
>> +             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) {
>> --
>> 2.9.3
>>
>
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