[PATCH v2 3/4] drm/sun4i: tcon: Support the LVDS Dual-Link on the A20

[Laurent Pinchart]

Hi Maxime,

Thank you for the patch.

On Thu, Jul 30, 2020 at 11:35:03AM +0200, Maxime Ripard wrote:
> The A20 can use its second TCON as the secondary LVDS link in a dual-link
> setup, with the TCON0 being the main link. Extend a bit the parsing code to
> leverage the DRM dual-link code, register only the LVDS output on the
> primary TCON, and add the needed bits to setup the TCON properly.
> 
> Signed-off-by: Maxime Ripard <maxime at cerno.tech>
> ---
>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 36 +++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/sun4i/sun4i_tcon.h |  4 +++-
>  2 files changed, 40 insertions(+)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index d03ad75f9900..ed2abf6eb18b 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -487,6 +487,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
>  	else
>  		reg |= SUN4I_TCON0_LVDS_IF_DATA_POL_NORMAL;
>  
> +	if (tcon->lvds_dual_link)
> +		reg |= SUN4I_TCON0_LVDS_IF_DUAL_LINK;
> +
>  	if (sun4i_tcon_get_pixel_depth(encoder) == 24)
>  		reg |= SUN4I_TCON0_LVDS_IF_BITWIDTH_24BITS;
>  	else
> @@ -896,6 +899,16 @@ static int sun4i_tcon_register_panel(struct drm_device *drm,
>  		return sun4i_rgb_init(drm, tcon);
>  
>  	/*
> +	 * Only the TCON0 will be relevant for the LVDS output, so if
> +	 * our ID is something else, let's prevent our TCON from
> +	 * registering its own LVDS output
> +	 */
> +	if (tcon->id) {
> +		dev_info(dev, "Secondary TCON, disabling panel output");

This may worry the user unnecessarily. I'd make it a debug message, or
drop it completely, and like reword it a bit as pointed out by Chen-Yu.

> +		return 0;
> +	}
> +
> +	/*
>  	 * This can only be made optional since we've had DT
>  	 * nodes without the LVDS reset properties.
>  	 *
> @@ -941,6 +954,28 @@ static int sun4i_tcon_register_panel(struct drm_device *drm,
>  		return -ENODEV;
>  	}
>  
> +	/*
> +	 * If we don't have a second TCON, we will never be able to do
> +	 * dual-link LVDS, so we don't have much more to do.
> +	 */
> +	companion = of_parse_phandle(dev->of_node, "allwinner,lvds-companion", 0);

Should there be a patch to add this property to the DT bindings ?

> +	if (!companion)
> +		return 0;
> +
> +	/*
> +	 * Let's do a sanity check on the dual-link setup to make sure
> +	 * everything is properly described.
> +	 */
> +	ret = drm_of_lvds_get_dual_link_pixel_order(dev->of_node, 1, 0,
> +						    companion, 1, 0);
> +	if (ret < 0) {
> +		dev_err(dev, "Invalid Dual-Link Configuration.\n");
> +		return ret;
> +	}
> +
> +	dev_info(dev, "Primary TCON, enabling LVDS Dual-Link");
> +	tcon->lvds_dual_link = true;
> +
>  	return sun4i_lvds_init(drm, tcon);
>  }
>  
> @@ -1500,6 +1535,7 @@ static const struct sun4i_tcon_quirks sun7i_a20_tcon0_quirks = {
>  };
>  
>  static const struct sun4i_tcon_quirks sun7i_a20_quirks = {
> +	.supports_lvds		= true,

Should this be split to a separate patch, or at least mentioned in the
commit message ?

>  	.has_channel_0		= true,
>  	.has_channel_1		= true,
>  	.dclk_min_div		= 4,
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h
> index cfbf4e6c1679..51c4e09cdd13 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
> @@ -98,6 +98,7 @@
>  
>  #define SUN4I_TCON0_LVDS_IF_REG			0x84
>  #define SUN4I_TCON0_LVDS_IF_EN				BIT(31)
> +#define SUN4I_TCON0_LVDS_IF_DUAL_LINK			BIT(30)
>  #define SUN4I_TCON0_LVDS_IF_BITWIDTH_MASK		BIT(26)
>  #define SUN4I_TCON0_LVDS_IF_BITWIDTH_18BITS		(1 << 26)
>  #define SUN4I_TCON0_LVDS_IF_BITWIDTH_24BITS		(0 << 26)
> @@ -274,6 +275,9 @@ struct sun4i_tcon {
>  	/* Associated crtc */
>  	struct sun4i_crtc		*crtc;
>  
> +	/* Is the LVDS link a dual-channel link? */
> +	bool				lvds_dual_link;
> +
>  	int				id;
>  
>  	/* TCON list management */

-- 
Regards,

Laurent Pinchart