linux-kernel - RE: [PATCH] drm: rcar_lvds: Fix dual link mode operations

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Message-ID: <TY1PR01MB1770980628C5914BC796C47FC0C60@TY1PR01MB1770.jpnprd01.prod.outlook.com>
Date:   Wed, 24 Jul 2019 08:10:22 +0000
From:   Fabrizio Castro <fabrizio.castro@...renesas.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
CC:     "open list:DRM DRIVERS FOR RENESAS" <dri-devel@...ts.freedesktop.org>,
        "open list:DRM DRIVERS FOR RENESAS" 
        <linux-renesas-soc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] drm: rcar_lvds: Fix dual link mode operations

Hi Jacopo,

Thank you for your patch!

> From: linux-renesas-soc-owner@...r.kernel.org <linux-renesas-soc-owner@...r.kernel.org> On Behalf Of Jacopo Mondi
> Sent: 23 July 2019 17:57
> Subject: [PATCH] drm: rcar_lvds: Fix dual link mode operations
> 
> The R-Car LVDS encoder units support dual-link operations by splitting
> the pixel output between the primary encoder and the companion one.
> 
> In order for the primary encoder to succesfully control the companion's
> operations this should not fail at probe time and register itself its
> associated drm bridge so that the primary one can find it.
> 
> Currently the companion encoder fails at probe time, causing the
> registration of the primary to fail preventing the whole DU unit to be
> registered correctly.
> 
> Fixes: fa440d870358 ("drm: rcar-du: lvds: Add support for dual-link mode")
> Reported-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

Reviewed-by: Fabrizio Castro <fabrizio.castro@...renesas.com>
Tested-by: Fabrizio Castro <fabrizio.castro@...renesas.com>

> 
> ---
> The "Fixes" tag refers to a patch currently part of the
> renesas-drivers-2019-07-09-v5.2 branch of Geert's renesas-drivers tree.
> 
>  drivers/gpu/drm/rcar-du/rcar_lvds.c | 31 +++++++++++++++++++++--------
>  1 file changed, 23 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> index bada7ee98544..8b015ba95895 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
> @@ -767,14 +767,29 @@ static int rcar_lvds_parse_dt(struct rcar_lvds *lvds)
>  	of_node_put(remote_input);
>  	of_node_put(remote);
> 
> -	/*
> -	 * On D3/E3 the LVDS encoder provides a clock to the DU, which can be
> -	 * used for the DPAD output even when the LVDS output is not connected.
> -	 * Don't fail probe in that case as the DU will need the bridge to
> -	 * control the clock.
> -	 */
> -	if (lvds->info->quirks & RCAR_LVDS_QUIRK_EXT_PLL)
> -		return ret == -ENODEV ? 0 : ret;
> +	switch (ret) {
> +	case -ENODEV:
> +		/*
> +		 * On D3/E3 the LVDS encoder provides a clock to the DU, which
> +		 * can be used for the DPAD output even when the LVDS output is
> +		 * not connected. Don't fail probe in that case as the DU will
> +		 * need the bridge to control the clock.
> +		 */
> +		if (lvds->info->quirks & RCAR_LVDS_QUIRK_EXT_PLL)
> +			ret = 0;
> +		break;
> +	case -ENXIO:
> +		/*
> +		 * When the LVDS output is used in dual link mode, the
> +		 * companion encoder fails at
> +		 * 'rcar_lvds_parse_dt_companion()'. Don't fail probe in
> +		 * that case as the master encoder will need the companion's
> +		 * bridge to control its operations.
> +		 */
> +		if (lvds->info->quirks & RCAR_LVDS_QUIRK_DUAL_LINK)
> +			ret = 0;
> +		break;
> +	}
> 
>  	return ret;
>  }
> --
> 2.22.0