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Message-ID: <8cda4dc8-8804-c34c-3a64-53c0ee01f2e8@codeaurora.org>
Date: Wed, 16 Nov 2016 13:47:03 +0530
From: Archit Taneja <architt@...eaurora.org>
To: Chen-Yu Tsai <wens@...e.org>
Cc: David Airlie <airlied@...ux.ie>, Rob Herring <robh@...nel.org>,
Maxime Ripard <maxime.ripard@...e-electrons.com>,
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
Hi,
On 11/15/2016 08:29 AM, Chen-Yu Tsai wrote:
> Hi,
>
> On Wed, Nov 2, 2016 at 9:33 AM, Chen-Yu Tsai <wens@...e.org> wrote:
>> 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>
>
> Any comments on this patch from the DRM people?
A comment below.
>
> ChenYu
>
>>>
>>> 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);
A cleaner way would be to set vga->vdd to NULL here, and do:
int ret = 0;
if (vga->vdd)
ret = regulator_enable(vga->vdd);
if (ret) {
...
return;
}
/* if a gpio is added later */
if (vga->gpio)
ret = gpiod_set_value_cansleep(vga->gpio, 1);
if (ret) {
...
return;
}
...
We don't really care what error code is contained in vga->vdd once we have
identified whether we got a regulator or not.
The same thing can be done for ddc too, but that can done left for later.
If you're okay with the suggestion, can you re-spin a patch?
Thanks,
Archit
>>>> + }
>>>> +
>>>> 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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