Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933885AbcJ0GlN (ORCPT ); Thu, 27 Oct 2016 02:41:13 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:37046 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932605AbcJ0GlK (ORCPT ); Thu, 27 Oct 2016 02:41:10 -0400 DMARC-Filter: OpenDMARC Filter v1.3.1 smtp.codeaurora.org 7B31E6161D Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=pass smtp.mailfrom=architt@codeaurora.org From: Archit Taneja Subject: Re: [PATCH v2 1/8] drm/bridge: rgb-to-vga: Support an enable GPIO To: Chen-Yu Tsai , Laurent Pinchart References: <20161020034344.14154-1-wens@csie.org> <20161020034344.14154-2-wens@csie.org> <0b5fbe8e-e51b-c874-e1a3-0b88dc65e361@codeaurora.org> Cc: Maxime Ripard , David Airlie , Rob Herring , Mark Rutland , devicetree , linux-sunxi , dri-devel , linux-kernel , linux-arm-kernel , Rob Herring Message-ID: <87ca071d-c396-25b3-aff4-c838c9003f94@codeaurora.org> Date: Thu, 27 Oct 2016 12:10:42 +0530 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5171 Lines: 158 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? > 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. 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