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Subject: Re: [PATCH v2 2/3] drm: bridge: Add LVDS decoder driver
To:     Jacopo Mondi <jacopo+renesas@jmondi.org>, <architt@codeaurora.org>,
        <a.hajda@samsung.com>, <Laurent.pinchart@ideasonboard.com>,
        <airlied@linux.ie>, <horms@verge.net.au>, <magnus.damm@gmail.com>,
        <geert@linux-m68k.org>, <niklas.soderlund@ragnatech.se>,
        <sergei.shtylyov@cogentembedded.com>, <robh+dt@kernel.org>,
        <mark.rutland@arm.com>
References: <1520603500-15218-1-git-send-email-jacopo+renesas@jmondi.org>
 <1520603500-15218-3-git-send-email-jacopo+renesas@jmondi.org>
CC:     <dri-devel@lists.freedesktop.org>,
        <linux-renesas-soc@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
From:   Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Message-ID: <dc468964-dc9c-65fb-7ec8-e180409ffa03@mentor.com>
Date:   Tue, 20 Mar 2018 17:42:59 +0200
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Hi Jacopo,

On 03/09/2018 03:51 PM, Jacopo Mondi wrote:
> Add transparent LVDS decoder driver.
> 
> A transparent LVDS decoder is a DRM bridge device that does not require
> any configuration and converts LVDS input to digital CMOS/TTL parallel
> data output.
> 
> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
>  drivers/gpu/drm/bridge/Kconfig        |   8 +++
>  drivers/gpu/drm/bridge/Makefile       |   1 +
>  drivers/gpu/drm/bridge/lvds-decoder.c | 129 ++++++++++++++++++++++++++++++++++
>  3 files changed, 138 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/lvds-decoder.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 3b99d5a..e52a5af 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -32,6 +32,14 @@ config DRM_DUMB_VGA_DAC
>  	help
>  	  Support for RGB to VGA DAC based bridges
> 
> +config DRM_LVDS_DECODER
> +	tristate "Transparent LVDS to parallel decoder support"
> +	depends on OF
> +	select DRM_PANEL_BRIDGE
> +	help
> +	  Support for transparent LVDS to parallel decoders that don't require
> +	  any configuration.
> +
>  config DRM_LVDS_ENCODER
>  	tristate "Transparent parallel to LVDS encoder support"
>  	depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 373eb28..edc2332 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -1,6 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>  obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
> +obj-$(CONFIG_DRM_LVDS_DECODER) += lvds-decoder.o
>  obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
>  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
> diff --git a/drivers/gpu/drm/bridge/lvds-decoder.c b/drivers/gpu/drm/bridge/lvds-decoder.c
> new file mode 100644
> index 0000000..319f4d5
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/lvds-decoder.c
> @@ -0,0 +1,129 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * LVDS to parallel data DRM bridge driver.
> + *
> + * Copyright (C) 2018 Jacopo Mondi <jacopo+renesas@jmondi.org>
> + */
> +
> +#include <drm/drmP.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_panel.h>
> +
> +#include <linux/of_graph.h>
> +
> +struct lvds_decoder {
> +	struct device *dev;
> +
> +	struct drm_bridge bridge;
> +	struct drm_bridge *next;
> +	struct drm_encoder *bridge_encoder;
> +};
> +
> +static inline struct lvds_decoder *to_lvds_decoder(struct drm_bridge *bridge)
> +{
> +	return container_of(bridge, struct lvds_decoder, bridge);
> +}
> +
> +static int lvds_decoder_attach(struct drm_bridge *bridge)
> +{
> +	struct lvds_decoder *lvds = to_lvds_decoder(bridge);
> +
> +	return drm_bridge_attach(bridge->encoder, lvds->next, bridge);
> +}
> +
> +struct drm_bridge_funcs lvds_dec_bridge_func = {

static const struct drm_bridge_funcs lvds_dec_bridge_func

> +	.attach	= lvds_decoder_attach,
> +};
> +
> +static int lvds_decoder_parse_dt(struct lvds_decoder *lvds)
> +{
> +	struct device_node *lvds_output;
> +	struct device_node *remote;
> +	int ret = 0;
> +
> +	lvds_output = of_graph_get_endpoint_by_regs(lvds->dev->of_node, 1, -1);
> +	if (!lvds_output) {
> +		dev_err(lvds->dev, "Missing endpoint in Port@1\n");
> +		return -ENODEV;
> +	}
> +
> +	remote = of_graph_get_remote_port_parent(lvds_output);

Add of_node_put(lvds_output) right here to get rid of error_put_lvds_node
goto label.

> +	if (!remote) {
> +		dev_err(lvds->dev, "Endpoint in Port@1 unconnected\n");
> +		ret = -ENODEV;
> +		goto error_put_lvds_node;
> +	}
> +
> +	if (!of_device_is_available(remote)) {
> +		dev_err(lvds->dev, "Port@1 remote endpoint is disabled\n");
> +		ret = -ENODEV;
> +		goto error_put_remote_node;
> +	}
> +
> +	lvds->next = of_drm_find_bridge(remote);
> +	if (!lvds->next)
> +		ret = -EPROBE_DEFER;
> +
> +error_put_remote_node:
> +	of_node_put(remote);
> +error_put_lvds_node:
> +	of_node_put(lvds_output);
> +
> +	return ret;
> +}
> +
> +static int lvds_decoder_probe(struct platform_device *pdev)
> +{
> +	struct lvds_decoder *lvds;
> +	int ret;
> +
> +	lvds = devm_kzalloc(&pdev->dev, sizeof(*lvds), GFP_KERNEL);
> +	if (!lvds)
> +		return -ENOMEM;
> +
> +	lvds->dev = &pdev->dev;
> +	platform_set_drvdata(pdev, lvds);
> +
> +	ret = lvds_decoder_parse_dt(lvds);
> +	if (ret)
> +		return ret;
> +
> +	lvds->bridge.driver_private = lvds;
> +	lvds->bridge.of_node = pdev->dev.of_node;
> +	lvds->bridge.funcs = &lvds_dec_bridge_func;
> +
> +	drm_bridge_add(&lvds->bridge);
> +
> +	return 0;
> +}
> +
> +static int lvds_decoder_remove(struct platform_device *pdev)
> +{
> +	struct lvds_decoder *lvds = platform_get_drvdata(pdev);
> +
> +	drm_bridge_remove(&lvds->bridge);
> +
> +	return 0;
> +}
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id lvds_decoder_match[] = {
> +	{ .compatible = "lvds-decoder", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, lvds_decoder_match);
> +#endif
> +

I would say "#ifdef CONFIG_OF" is redundant, because the driver "depends on OF".

> +static struct platform_driver lvds_decoder_driver = {
> +	.probe	= lvds_decoder_probe,
> +	.remove	= lvds_decoder_remove,
> +	.driver	= {
> +		.name		= "lvds_decoder",
> +		.of_match_table	= lvds_decoder_match,
> +	},
> +};
> +module_platform_driver(lvds_decoder_driver);
> +
> +MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>");
> +MODULE_DESCRIPTION("Transparent LVDS to parallel data decoder");
> +MODULE_LICENSE("GPL v2");

--
With best wishes,
Vladimir