linux-kernel - Re: [PATCH 5/5] drm/bridge: nwl-dsi: add support for DCSS

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Date:   Fri, 4 Sep 2020 19:05:01 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     "Robert Chiras (OSS)" <robert.chiras@....nxp.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Fabio Estevam <festevam@...il.com>,
        Ondrej Jirman <megous@...ous.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-imx@....com
Subject: Re: [PATCH 5/5] drm/bridge: nwl-dsi: add support for DCSS

Hi,
On Fri, Aug 28, 2020 at 02:13:32PM +0300, Robert Chiras (OSS) wrote:
> From: Laurentiu Palcu <laurentiu.palcu@....com>
> 
> DCSS needs active low VSYNC and HSYNC. Also, move the input selection in
> the probe function, as this will not change at runtime.
> 
> Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....com>
> Signed-off-by: Robert Chiras <robert.chiras@....com>
> ---
>  drivers/gpu/drm/bridge/nwl-dsi.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/nwl-dsi.c b/drivers/gpu/drm/bridge/nwl-dsi.c
> index ac4aa0a..c30f7a8 100644
> --- a/drivers/gpu/drm/bridge/nwl-dsi.c
> +++ b/drivers/gpu/drm/bridge/nwl-dsi.c
> @@ -143,6 +143,7 @@ struct nwl_dsi {
>  	struct nwl_dsi_transfer *xfer;
>  	struct list_head valid_modes;
>  	u32 clk_drop_lvl;
> +	bool use_dcss;
>  };
>  
>  static const struct regmap_config nwl_dsi_regmap_config = {
> @@ -1036,16 +1037,16 @@ static int nwl_dsi_get_dphy_params(struct nwl_dsi *dsi,
>  
>  static bool nwl_dsi_bridge_mode_fixup(struct drm_bridge *bridge,
>  				      const struct drm_display_mode *mode,
> -				      struct drm_display_mode *adjusted_mode)
> +				      struct drm_display_mode *adjusted)

why the rename?

>  {
>  	struct nwl_dsi *dsi = bridge_to_dsi(bridge);
>  	struct mode_config *config;
>  	unsigned long pll_rate;
>  
>  	DRM_DEV_DEBUG_DRIVER(dsi->dev, "Fixup mode:\n");
> -	drm_mode_debug_printmodeline(adjusted_mode);
> +	drm_mode_debug_printmodeline(adjusted);
>  
> -	config = nwl_dsi_mode_probe(dsi, adjusted_mode);
> +	config = nwl_dsi_mode_probe(dsi, adjusted);
>  	if (!config)
>  		return false;
>  
> @@ -1067,12 +1068,16 @@ static bool nwl_dsi_bridge_mode_fixup(struct drm_bridge *bridge,
>  	}
>  	/* Update the crtc_clock to be used by display controller */
>  	if (config->crtc_clock)
> -		adjusted_mode->crtc_clock = config->crtc_clock / 1000;
> +		adjusted->crtc_clock = config->crtc_clock / 1000;
>  
> -
> -	/* At least LCDIF + NWL needs active high sync */
> -	adjusted_mode->flags |= (DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC);
> -	adjusted_mode->flags &= ~(DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC);
> +	if (!dsi->use_dcss) {
> +		/* At least LCDIF + NWL needs active high sync */
> +		adjusted->flags |= (DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC);
> +		adjusted->flags &= ~(DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC);
> +	} else {
> +		adjusted->flags &= ~(DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC);
> +		adjusted->flags |= (DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC);
> +	}
>  
>  	return true;
>  }
> @@ -1400,6 +1405,9 @@ static int nwl_dsi_select_input(struct nwl_dsi *dsi)
>  		DRM_DEV_ERROR(dsi->dev, "Failed to select input: %d\n", ret);
>  
>  	of_node_put(remote);
> +
> +	dsi->use_dcss = use_dcss;

If we need to preserve it we can assign `dsi->use_dcss` directly and
drop `use_dcss`.
Cheers,
 -- Guido

> +
>  	return ret;
>  }
>  
> -- 
> 2.7.4
>