Re: [PATCH v2 1/4] drm/bridge: Repurpose lvds-encoder.c

From: Jacopo Mondi <jacopo@jmondi.org>
To: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Andrzej Hajda <a.hajda@samsung.com>,
	Simon Horman <horms@verge.net.au>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Magnus Damm <magnus.damm@gmail.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Peter Rosin <peda@axentia.se>,
	dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
	linux-renesas-soc@vger.kernel.org,
	Chris Paterson <Chris.Paterson2@renesas.com>,
	Biju Das <biju.das@bp.renesas.com>,
	Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
	Jacopo Mondi <jacopo+renesas@jmondi.org>
Subject: Re: [PATCH v2 1/4] drm/bridge: Repurpose lvds-encoder.c
Date: Thu, 7 Nov 2019 19:19:20 +0100	[thread overview]
Message-ID: <20191107181920.yh2suj3e2gra3iip@uno.localdomain> (raw)
In-Reply-To: <1572886683-4919-2-git-send-email-fabrizio.castro@bp.renesas.com>

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Hi Fabrizio,
  thanks for the patch.

On Mon, Nov 04, 2019 at 04:58:00PM +0000, Fabrizio Castro wrote:
> lvds-encoder.c implementation is also suitable for LVDS decoders,
> not just LVDS encoders.
> Instead of creating a new driver for addressing support for
> transparent LVDS decoders, repurpose lvds-encoder.c for the greater
> good.
>
> Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
>
> ---
> v1->v2:
> * No change
> ---
>  drivers/gpu/drm/bridge/Kconfig        |   8 +-
>  drivers/gpu/drm/bridge/Makefile       |   2 +-
>  drivers/gpu/drm/bridge/lvds-codec.c   | 169 ++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/bridge/lvds-encoder.c | 155 -------------------------------
>  4 files changed, 174 insertions(+), 160 deletions(-)
>  create mode 100644 drivers/gpu/drm/bridge/lvds-codec.c
>  delete mode 100644 drivers/gpu/drm/bridge/lvds-encoder.c
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 3436297..9e75ca4e 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -45,14 +45,14 @@ config DRM_DUMB_VGA_DAC
>  	  Support for non-programmable RGB to VGA DAC bridges, such as ADI
>  	  ADV7123, TI THS8134 and THS8135 or passive resistor ladder DACs.
>
> -config DRM_LVDS_ENCODER
> -	tristate "Transparent parallel to LVDS encoder support"
> +config DRM_LVDS_CODEC
> +	tristate "Transparent LVDS encoders and decoders support"
>  	depends on OF
>  	select DRM_KMS_HELPER
>  	select DRM_PANEL_BRIDGE
>  	help
> -	  Support for transparent parallel to LVDS encoders that don't require
> -	  any configuration.
> +	  Support for transparent LVDS encoders and LVDS decoders that don't
> +	  require any configuration.
>
>  config DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW
>  	tristate "MegaChips stdp4028-ge-b850v3-fw and stdp2690-ge-b850v3-fw"
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 4934fcf..8a9178a 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -2,7 +2,7 @@
>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
>  obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
> -obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
> +obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
>  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
>  obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> new file mode 100644
> index 0000000..8a1979c
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> @@ -0,0 +1,169 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2016 Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> + */
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_panel.h>
> +
> +struct lvds_codec {
> +	struct drm_bridge bridge;
> +	struct drm_bridge *panel_bridge;
> +	struct gpio_desc *powerdown_gpio;
> +	u32 connector_type;
> +};
> +
> +static int lvds_codec_attach(struct drm_bridge *bridge)
> +{
> +	struct lvds_codec *lvds_codec = container_of(bridge,
> +							 struct lvds_codec,
> +							 bridge);
> +

Weird indentation. Align to open ( to match the rest of the driver's
style.

> +	return drm_bridge_attach(bridge->encoder, lvds_codec->panel_bridge,
> +				 bridge);
> +}
> +
> +static void lvds_codec_enable(struct drm_bridge *bridge)
> +{
> +	struct lvds_codec *lvds_codec = container_of(bridge,
> +							 struct lvds_codec,
> +							 bridge);
> +

Here too

> +	if (lvds_codec->powerdown_gpio)
> +		gpiod_set_value_cansleep(lvds_codec->powerdown_gpio, 0);
> +}
> +
> +static void lvds_codec_disable(struct drm_bridge *bridge)
> +{
> +	struct lvds_codec *lvds_codec = container_of(bridge,
> +							 struct lvds_codec,
> +							 bridge);
> +
> +	if (lvds_codec->powerdown_gpio)
> +		gpiod_set_value_cansleep(lvds_codec->powerdown_gpio, 1);
> +}
> +
> +static struct drm_bridge_funcs funcs = {
> +	.attach = lvds_codec_attach,
> +	.enable = lvds_codec_enable,
> +	.disable = lvds_codec_disable,
> +};
> +
> +static int lvds_codec_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *port;
> +	struct device_node *endpoint;
> +	struct device_node *panel_node;
> +	struct drm_panel *panel;
> +	struct lvds_codec *lvds_codec;
> +
> +	lvds_codec = devm_kzalloc(dev, sizeof(*lvds_codec), GFP_KERNEL);
> +	if (!lvds_codec)
> +		return -ENOMEM;
> +
> +	lvds_codec->connector_type = (u32)
> +		of_device_get_match_data(&pdev->dev);

Fits in 1 line

> +	lvds_codec->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown",
> +							       GPIOD_OUT_HIGH);
> +	if (IS_ERR(lvds_codec->powerdown_gpio)) {
> +		int err = PTR_ERR(lvds_codec->powerdown_gpio);
> +
> +		if (err != -EPROBE_DEFER)
> +			dev_err(dev, "powerdown GPIO failure: %d\n", err);
> +		return err;

I know it was there already, but this seems a bit unusual for the
minimal gain of having a printout in the very unlikely case the
gpiod_get() operations fails. I would just return PTR_ERR().

> +	}
> +
> +	/* Locate the panel DT node. */
> +	port = of_graph_get_port_by_id(dev->of_node, 1);
> +	if (!port) {
> +		dev_dbg(dev, "port 1 not found\n");
> +		return -ENXIO;
> +	}
> +
> +	endpoint = of_get_child_by_name(port, "endpoint");
> +	of_node_put(port);
> +	if (!endpoint) {
> +		dev_dbg(dev, "no endpoint for port 1\n");
> +		return -ENXIO;
> +	}

I know it was there already, but this could be simplified with
of_graph_get_endpoint_by_regs()
> +
> +	panel_node = of_graph_get_remote_port_parent(endpoint);
> +	of_node_put(endpoint);
> +	if (!panel_node) {
> +		dev_dbg(dev, "no remote endpoint for port 1\n");
> +		return -ENXIO;
> +	}

Or even better, simplify these three with of_graph_get_remote_node()

> +
> +	panel = of_drm_find_panel(panel_node);
> +	of_node_put(panel_node);
> +	if (IS_ERR(panel)) {
> +		dev_dbg(dev, "panel not found, deferring probe\n");
> +		return PTR_ERR(panel);
> +	}
> +
> +	lvds_codec->panel_bridge =
> +		devm_drm_panel_bridge_add_typed(dev, panel,
> +						lvds_codec->connector_type);

The function documentation reports this as deprecated and suggested to
use the non-typed version. Do you think it could work for this new
codec driver ?

> +	if (IS_ERR(lvds_codec->panel_bridge))
> +		return PTR_ERR(lvds_codec->panel_bridge);
> +
> +	/* The panel_bridge bridge is attached to the panel's of_node,
> +	 * but we need a bridge attached to our of_node for our user
> +	 * to look up.
> +	 */
> +	lvds_codec->bridge.of_node = dev->of_node;
> +	lvds_codec->bridge.funcs = &funcs;
> +	drm_bridge_add(&lvds_codec->bridge);
> +
> +	platform_set_drvdata(pdev, lvds_codec);
> +
> +	return 0;
> +}
> +
> +static int lvds_codec_remove(struct platform_device *pdev)
> +{
> +	struct lvds_codec *lvds_codec = platform_get_drvdata(pdev);
> +
> +	drm_bridge_remove(&lvds_codec->bridge);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id lvds_codec_match[] = {
> +	{
> +		.compatible = "lvds-encoder",
> +		.data = (void *)DRM_MODE_CONNECTOR_LVDS

In case you for for drm_panel_bridge_add() you could drop the type

> +	},
> +	{
> +		.compatible = "thine,thc63lvdm83d",
> +		.data = (void *)DRM_MODE_CONNECTOR_LVDS,
> +	},
> +	{
> +		.compatible = "lvds-decoder",
> +		.data = (void *)DRM_MODE_CONNECTOR_Unknown,
> +	},

Which decoder are you using? This is a generic fallback, but I would
expect compatible for a real device to appear in DTS.

> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, lvds_codec_match);
> +
> +static struct platform_driver lvds_codec_driver = {
> +	.probe	= lvds_codec_probe,
> +	.remove	= lvds_codec_remove,
> +	.driver		= {
> +		.name		= "lvds-codec",
> +		.of_match_table	= lvds_codec_match,
> +	},
> +};
> +module_platform_driver(lvds_codec_driver);
> +
> +MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
> +MODULE_DESCRIPTION("Driver for transparent LVDS encoders and LVDS decoders");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/gpu/drm/bridge/lvds-encoder.c b/drivers/gpu/drm/bridge/lvds-encoder.c
> deleted file mode 100644
> index e2132a8..0000000
> --- a/drivers/gpu/drm/bridge/lvds-encoder.c
> +++ /dev/null
> @@ -1,155 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0-or-later
> -/*
> - * Copyright (C) 2016 Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> - */
> -
> -#include <linux/gpio/consumer.h>
> -#include <linux/module.h>
> -#include <linux/of.h>
> -#include <linux/of_graph.h>
> -#include <linux/platform_device.h>
> -
> -#include <drm/drm_bridge.h>
> -#include <drm/drm_panel.h>
> -
> -struct lvds_encoder {
> -	struct drm_bridge bridge;
> -	struct drm_bridge *panel_bridge;
> -	struct gpio_desc *powerdown_gpio;
> -};
> -
> -static int lvds_encoder_attach(struct drm_bridge *bridge)
> -{
> -	struct lvds_encoder *lvds_encoder = container_of(bridge,
> -							 struct lvds_encoder,
> -							 bridge);
> -
> -	return drm_bridge_attach(bridge->encoder, lvds_encoder->panel_bridge,
> -				 bridge);
> -}
> -
> -static void lvds_encoder_enable(struct drm_bridge *bridge)
> -{
> -	struct lvds_encoder *lvds_encoder = container_of(bridge,
> -							 struct lvds_encoder,
> -							 bridge);
> -
> -	if (lvds_encoder->powerdown_gpio)
> -		gpiod_set_value_cansleep(lvds_encoder->powerdown_gpio, 0);
> -}
> -
> -static void lvds_encoder_disable(struct drm_bridge *bridge)
> -{
> -	struct lvds_encoder *lvds_encoder = container_of(bridge,
> -							 struct lvds_encoder,
> -							 bridge);
> -
> -	if (lvds_encoder->powerdown_gpio)
> -		gpiod_set_value_cansleep(lvds_encoder->powerdown_gpio, 1);
> -}
> -
> -static struct drm_bridge_funcs funcs = {
> -	.attach = lvds_encoder_attach,
> -	.enable = lvds_encoder_enable,
> -	.disable = lvds_encoder_disable,
> -};
> -
> -static int lvds_encoder_probe(struct platform_device *pdev)
> -{
> -	struct device *dev = &pdev->dev;
> -	struct device_node *port;
> -	struct device_node *endpoint;
> -	struct device_node *panel_node;
> -	struct drm_panel *panel;
> -	struct lvds_encoder *lvds_encoder;
> -
> -	lvds_encoder = devm_kzalloc(dev, sizeof(*lvds_encoder), GFP_KERNEL);
> -	if (!lvds_encoder)
> -		return -ENOMEM;
> -
> -	lvds_encoder->powerdown_gpio = devm_gpiod_get_optional(dev, "powerdown",
> -							       GPIOD_OUT_HIGH);
> -	if (IS_ERR(lvds_encoder->powerdown_gpio)) {
> -		int err = PTR_ERR(lvds_encoder->powerdown_gpio);
> -
> -		if (err != -EPROBE_DEFER)
> -			dev_err(dev, "powerdown GPIO failure: %d\n", err);
> -		return err;
> -	}
> -
> -	/* Locate the panel DT node. */
> -	port = of_graph_get_port_by_id(dev->of_node, 1);
> -	if (!port) {
> -		dev_dbg(dev, "port 1 not found\n");
> -		return -ENXIO;
> -	}
> -
> -	endpoint = of_get_child_by_name(port, "endpoint");
> -	of_node_put(port);
> -	if (!endpoint) {
> -		dev_dbg(dev, "no endpoint for port 1\n");
> -		return -ENXIO;
> -	}
> -
> -	panel_node = of_graph_get_remote_port_parent(endpoint);
> -	of_node_put(endpoint);
> -	if (!panel_node) {
> -		dev_dbg(dev, "no remote endpoint for port 1\n");
> -		return -ENXIO;
> -	}
> -
> -	panel = of_drm_find_panel(panel_node);
> -	of_node_put(panel_node);
> -	if (IS_ERR(panel)) {
> -		dev_dbg(dev, "panel not found, deferring probe\n");
> -		return PTR_ERR(panel);
> -	}
> -
> -	lvds_encoder->panel_bridge =
> -		devm_drm_panel_bridge_add_typed(dev, panel,
> -						DRM_MODE_CONNECTOR_LVDS);
> -	if (IS_ERR(lvds_encoder->panel_bridge))
> -		return PTR_ERR(lvds_encoder->panel_bridge);
> -
> -	/* The panel_bridge bridge is attached to the panel's of_node,
> -	 * but we need a bridge attached to our of_node for our user
> -	 * to look up.
> -	 */
> -	lvds_encoder->bridge.of_node = dev->of_node;
> -	lvds_encoder->bridge.funcs = &funcs;
> -	drm_bridge_add(&lvds_encoder->bridge);
> -
> -	platform_set_drvdata(pdev, lvds_encoder);
> -
> -	return 0;
> -}
> -
> -static int lvds_encoder_remove(struct platform_device *pdev)
> -{
> -	struct lvds_encoder *lvds_encoder = platform_get_drvdata(pdev);
> -
> -	drm_bridge_remove(&lvds_encoder->bridge);
> -
> -	return 0;
> -}
> -
> -static const struct of_device_id lvds_encoder_match[] = {
> -	{ .compatible = "lvds-encoder" },
> -	{ .compatible = "thine,thc63lvdm83d" },
> -	{},
> -};
> -MODULE_DEVICE_TABLE(of, lvds_encoder_match);
> -
> -static struct platform_driver lvds_encoder_driver = {
> -	.probe	= lvds_encoder_probe,
> -	.remove	= lvds_encoder_remove,
> -	.driver		= {
> -		.name		= "lvds-encoder",
> -		.of_match_table	= lvds_encoder_match,
> -	},
> -};
> -module_platform_driver(lvds_encoder_driver);
> -
> -MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
> -MODULE_DESCRIPTION("Transparent parallel to LVDS encoder");
> -MODULE_LICENSE("GPL");
> --
> 2.7.4
>

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