Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934248AbcJ0GxM (ORCPT ); Thu, 27 Oct 2016 02:53:12 -0400 Received: from smtp.csie.ntu.edu.tw ([140.112.30.61]:60436 "EHLO smtp.csie.ntu.edu.tw" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932882AbcJ0GxJ (ORCPT ); Thu, 27 Oct 2016 02:53:09 -0400 MIME-Version: 1.0 In-Reply-To: <87ca071d-c396-25b3-aff4-c838c9003f94@codeaurora.org> References: <20161020034344.14154-1-wens@csie.org> <20161020034344.14154-2-wens@csie.org> <0b5fbe8e-e51b-c874-e1a3-0b88dc65e361@codeaurora.org> <87ca071d-c396-25b3-aff4-c838c9003f94@codeaurora.org> From: Chen-Yu Tsai Date: Thu, 27 Oct 2016 14:52:42 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 1/8] drm/bridge: rgb-to-vga: Support an enable GPIO To: Archit Taneja Cc: Chen-Yu Tsai , Laurent Pinchart , Maxime Ripard , David Airlie , Rob Herring , Mark Rutland , devicetree , linux-sunxi , dri-devel , linux-kernel , linux-arm-kernel Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5692 Lines: 182 On Thu, Oct 27, 2016 at 2:40 PM, Archit Taneja wrote: > > > On 10/25/2016 02:29 PM, Chen-Yu Tsai wrote: >> >> On Tue, Oct 25, 2016 at 4:09 PM, Archit Taneja >> wrote: >>> >>> Hi, >>> >>> On 10/20/2016 09:13 AM, Chen-Yu Tsai wrote: >>>> >>>> >>>> Some rgb-to-vga bridges have an enable GPIO, either directly tied to >>>> an enable pin on the bridge IC, or indirectly controlling a power >>>> switch. >>>> >>>> Add support for it. >>> >>> >>> >>> Does the bridge on your platform have an active/passive DAC, or is it a >>> smarter encoder chip that is capable of doing more? If so, it might be >>> good to have a separate DT compatible string to it, like what's done >>> in the patch titled: >>> >>> drm: bridge: vga-dac: Add adi,adv7123 compatible string >>> >>> so that we can switch to a different driver later if needed. >> >> >> The chip is GM7123. It is not configurable. It just takes the LCD RGB/SYNC >> signals and converts them to analog. The only things you can change are >> putting it into sleep mode and tweaking the output drive strength by > > > Is sleep mode the thing that's controlled by this gpio? Not on this particular board. The gpio controls the external LDO that supplies 3.3V to VDD. > >> changing the external reference resistor. The latter would be a hardware >> design decision. I would say this qualifies as "dumb". > > > Yeah, I agree. I'd want feedback from Laurent too, since he had comments > on the usage of the original dumb-vga-dac driver. > >> >> I revisited the board schematics, and the enable GPIO actually toggles >> an external LDO regulator. So this might be better modeled as a regulator >> supply? > > > If you model it as a regulator, how would you toggle the GPIO on your > platform? > > Looking at the chip pin out, there is a 3.3V VDD supply needed for the > chip, so it would be good to have an optional 'power' regulator supply > anyway. Yes, that it what I plan to do. I'll drop the enable-gpios property, and add a power-supply property for the regulator. Regards ChenYu > > Archit > > >> >> >> Thanks >> ChenYu >> >>> >>> Thanks, >>> Archit >>> >>> >>>> >>>> Signed-off-by: Chen-Yu Tsai >>>> --- >>>> .../bindings/display/bridge/dumb-vga-dac.txt | 2 ++ >>>> drivers/gpu/drm/bridge/dumb-vga-dac.c | 28 >>>> ++++++++++++++++++++++ >>>> 2 files changed, 30 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..d3484822bf77 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: >>>> +- enable-gpios: GPIO pin to enable or disable the bridge >>>> >>>> Example >>>> ------- >>>> diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c >>>> b/drivers/gpu/drm/bridge/dumb-vga-dac.c >>>> index afec232185a7..b487e5e9b56d 100644 >>>> --- a/drivers/gpu/drm/bridge/dumb-vga-dac.c >>>> +++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c >>>> @@ -10,6 +10,7 @@ >>>> * the License, or (at your option) any later version. >>>> */ >>>> >>>> +#include >>>> #include >>>> #include >>>> >>>> @@ -23,6 +24,7 @@ struct dumb_vga { >>>> struct drm_connector connector; >>>> >>>> struct i2c_adapter *ddc; >>>> + struct gpio_desc *enable_gpio; >>>> }; >>>> >>>> static inline struct dumb_vga * >>>> @@ -124,8 +126,26 @@ 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); >>>> + >>>> + if (vga->enable_gpio) >>>> + gpiod_set_value_cansleep(vga->enable_gpio, 1); >>>> +} >>>> + >>>> +static void dumb_vga_disable(struct drm_bridge *bridge) >>>> +{ >>>> + struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge); >>>> + >>>> + if (vga->enable_gpio) >>>> + gpiod_set_value_cansleep(vga->enable_gpio, 0); >>>> +} >>>> + >>>> 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 +189,14 @@ static int dumb_vga_probe(struct platform_device >>>> *pdev) >>>> return -ENOMEM; >>>> platform_set_drvdata(pdev, vga); >>>> >>>> + vga->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable", >>>> + GPIOD_OUT_LOW); >>>> + if (IS_ERR(vga->enable_gpio)) { >>>> + ret = PTR_ERR(vga->enable_gpio); >>>> + dev_err(&pdev->dev, "failed to request GPIO: %d\n", >>>> ret); >>>> + return ret; >>>> + } >>>> + >>>> vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev); >>>> if (IS_ERR(vga->ddc)) { >>>> if (PTR_ERR(vga->ddc) == -ENODEV) { >>>> >>> >>> -- >>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, >>> a Linux Foundation Collaborative Project > > > -- > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, > a Linux Foundation Collaborative Project