linux-kernel - Re: [PATCH v4 3/7] drm: rcar-du: lvds: Get dual link configuration from DT

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Message-ID: <20191213213010.GN4860@pendragon.ideasonboard.com>
Date:   Fri, 13 Dec 2019 23:30:10 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Fabrizio Castro <fabrizio.castro@...renesas.com>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Sean Paul <sean@...rly.run>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Simon Horman <horms@...ge.net.au>,
        Magnus Damm <magnus.damm@...il.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        ebiharaml@...linux.co.jp
Subject: Re: [PATCH v4 3/7] drm: rcar-du: lvds: Get dual link configuration
 from DT

Hi Fabrizio,

Thank you for the patch.

On Fri, Dec 06, 2019 at 04:32:50PM +0000, Fabrizio Castro wrote:
> For dual-LVDS configurations, it is now possible to mark the
> DT port nodes for the sink with boolean properties (like
> dual-lvds-even-pixels and dual-lvds-odd-pixels) to let drivers
> know the encoders need to be configured in dual-LVDS mode.
> 
> Rework the implementation of rcar_lvds_parse_dt_companion
> to make use of the DT markers while keeping backward
> compatibility.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
> 
> ---
> v3->v4:
> * New patch extracted from patch:
>   "drm: rcar-du: lvds: Add dual-LVDS panels support"
> ---
>  drivers/gpu/drm/rcar-du/rcar_lvds.c | 56 +++++++++++++++++++++++++++++++------
>  1 file changed, 47 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> index 3cb0a83..6c1f171 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> @@ -669,8 +669,10 @@ EXPORT_SYMBOL_GPL(rcar_lvds_dual_link);
>  static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
>  {
>  	const struct of_device_id *match;
> -	struct device_node *companion;
> +	struct device_node *companion, *p0, *p1;

Could you rename p0 and p1 to port0 and port1, and spit them to a
separate line of variable declaration ?

> +	struct rcar_lvds *companion_lvds;
>  	struct device *dev = lvds->dev;
> +	int dual_link;
>  	int ret = 0;
>  
>  	/* Locate the companion LVDS encoder for dual-link operation, if any. */
> @@ -689,13 +691,55 @@ static int rcar_lvds_parse_dt_companion(struct rcar_lvds *lvds)
>  		goto done;
>  	}
>  
> +	/*
> +	 * We need to work out if the sink is expecting us to function in
> +	 * dual-link mode. We do this by looking at the DT port nodes we are
> +	 * connected to, if they are marked as expecting even pixels and
> +	 * odd pixels than we need to enable vertical stripe output.
> +	 */
> +	p0 = of_graph_get_port_by_id(dev->of_node, 1);
> +	p1 = of_graph_get_port_by_id(companion, 1);
> +	dual_link = drm_of_lvds_get_dual_link_pixel_order(p0, p1);
> +	of_node_put(p0);
> +	of_node_put(p1);
> +	if (dual_link >= DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS) {
> +		lvds->dual_link = true;
> +	} else if (lvds->next_bridge && lvds->next_bridge->timings) {
> +		/*
> +		 * Early dual-link bridge specific implementations populate the
> +		 * timings field of drm_bridge, read the dual_link flag off the
> +		 * bridge directly for backward compatibility.
> +		 */
> +		lvds->dual_link = lvds->next_bridge->timings->dual_link;
> +	}
> +
> +	if (!lvds->dual_link) {
> +		dev_dbg(dev, "Single-link configuration detected\n");
> +		goto done;
> +	}
> +
>  	lvds->companion = of_drm_find_bridge(companion);
>  	if (!lvds->companion) {
>  		ret = -EPROBE_DEFER;
>  		goto done;
>  	}
>  
> -	dev_dbg(dev, "Found companion encoder %pOF\n", companion);
> +	dev_dbg(dev,
> +		"Dual-link configuration detected (companion encoder %pOF)\n",
> +		companion);
> +
> +	companion_lvds = bridge_to_rcar_lvds(lvds->companion);

Could you move this line after the FIXME comment ?

With these small issues fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> +
> +	/*
> +	 * FIXME: We should not be messing with the companion encoder private
> +	 * data from the primary encoder, we should rather let the companion
> +	 * encoder work things out on its own. However, the companion encoder
> +	 * doesn't hold a reference to the primary encoder, and
> +	 * drm_of_lvds_get_dual_link_pixel_order needs to be given references
> +	 * to the output ports of both encoders, therefore leave it like this
> +	 * for the time being.
> +	 */
> +	companion_lvds->dual_link = true;
>  
>  done:
>  	of_node_put(companion);
> @@ -739,13 +783,7 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
>  	if (ret)
>  		goto done;
>  
> -	if ((lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK) &&
> -	    lvds->next_bridge)
> -		lvds->dual_link = lvds->next_bridge->timings
> -				? lvds->next_bridge->timings->dual_link
> -				: false;
> -
> -	if (lvds->dual_link)
> +	if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK)
>  		ret = rcar_lvds_parse_dt_companion(lvds);
>  
>  done:

-- 
Regards,

Laurent Pinchart