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

[Chen-Yu Tsai <wens@csie.org>]

On Thu, Jul 30, 2020 at 5:35 PM Maxime Ripard <maxime@cerno.tech> 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@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");

Nit: "disabling" is a bit misleading.

Just stating that it is used as a secondary link

> +               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);
> +       if (!companion)
> +               return 0;

I assume you want

                return sun4i_lvds_init(drm, tcon);

otherwise single-link LVDS would not work anymore?


ChenYu

> +
> +       /*
> +        * 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,
>         .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 */
> --
> git-series 0.9.1