[RFC][PATCH] drm/bridge: lvds-codec: Add support for pixel data sampling edge select

[Laurent Pinchart]

Hi Marek,

Thank you for the patch.

On Sat, Oct 03, 2020 at 01:08:23AM +0200, Marek Vasut wrote:
> The OnSemi FIN3385 Parallel-to-LVDS encoder has a dedicated input line to
> select input pixel data sampling edge. Add DT property "pixelclk-active",
> same as the one used by display timings, and configure bus flags based on
> this DT property.

The feature looks good to me. I however wonder if we shouldn't use the
standard pclk-sample endpoint property (documented in [1]) instead of a
custom properly.

The DT bindings for the lvds-codec should be updated accordingly. And
the property should only be taken into account when operating in encoder
mode, as for decoder mode there's no polarity for the sampling of LVDS
signals, as you've explained in a reply to Sam.

[1] Documentation/devicetree/bindings/media/video-interfaces.txt

> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Alexandre Torgue <alexandre.torgue at st.com>
> Cc: Andrzej Hajda <a.hajda at samsung.com>
> Cc: Antonio Borneo <antonio.borneo at st.com>
> Cc: Benjamin Gaignard <benjamin.gaignard at st.com>
> Cc: Biju Das <biju.das.jz at bp.renesas.com>
> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Cc: Maxime Coquelin <mcoquelin.stm32 at gmail.com>
> Cc: Philippe Cornu <philippe.cornu at st.com>
> Cc: Sam Ravnborg <sam at ravnborg.org>
> Cc: Vincent Abriou <vincent.abriou at st.com>
> Cc: Yannick Fertre <yannick.fertre at st.com>
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-stm32 at st-md-mailman.stormreply.com
> To: dri-devel at lists.freedesktop.org
> ---
>  drivers/gpu/drm/bridge/lvds-codec.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/lvds-codec.c b/drivers/gpu/drm/bridge/lvds-codec.c
> index f52ccffc1bd1..bc941d4fb5b9 100644
> --- a/drivers/gpu/drm/bridge/lvds-codec.c
> +++ b/drivers/gpu/drm/bridge/lvds-codec.c
> @@ -19,6 +19,7 @@ struct lvds_codec {
>  	struct device *dev;
>  	struct drm_bridge bridge;
>  	struct drm_bridge *panel_bridge;
> +	struct drm_bridge_timings timings;
>  	struct regulator *vcc;
>  	struct gpio_desc *powerdown_gpio;
>  	u32 connector_type;
> @@ -80,6 +81,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
>  	struct device_node *panel_node;
>  	struct drm_panel *panel;
>  	struct lvds_codec *lvds_codec;
> +	u32 val;
>  	int ret;
>  
>  	lvds_codec = devm_kzalloc(dev, sizeof(*lvds_codec), GFP_KERNEL);
> @@ -124,6 +126,12 @@ static int lvds_codec_probe(struct platform_device *pdev)
>  	if (IS_ERR(lvds_codec->panel_bridge))
>  		return PTR_ERR(lvds_codec->panel_bridge);
>  
> +	if (!of_property_read_u32(dev->of_node, "pixelclk-active", &val)) {
> +		lvds_codec->timings.input_bus_flags = val ?
> +			DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE :
> +			DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE;
> +	}
> +
>  	/*
>  	 * 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
> @@ -131,6 +139,7 @@ static int lvds_codec_probe(struct platform_device *pdev)
>  	 */
>  	lvds_codec->bridge.of_node = dev->of_node;
>  	lvds_codec->bridge.funcs = &funcs;
> +	lvds_codec->bridge.timings = &lvds_codec->timings;
>  	drm_bridge_add(&lvds_codec->bridge);
>  
>  	platform_set_drvdata(pdev, lvds_codec);

-- 
Regards,

Laurent Pinchart