Re: [PATCH 04/13] drm/sun4i: tcon-top: Keep mixer routes distinct

On Tue, Aug 4, 2026 at 12:11 AM Jernej Skrabec <[email protected]> wrote:
>
> Both mixer selectors reset to TCON 0. Selecting the same TCON for both
> mixers causes black or corrupted output.
>
> When a route would collide, park the other mixer on another described
> TCON, or an unused selector if none exists.
>
> Since the TCON index is now used as a shift, also reject negative
> values.
>
> Tested on Orange Pi 3 with TCON_LCD0 and TCON_TV0.
>
> Link: https://lore.kernel.org/linux-sunxi/Zn8GVkpwXwhaUFno@titan/
> Link: https://lore.kernel.org/linux-sunxi/[email protected]/
> Fixes: 05db311a792d ("drm/sun4i: tcon-top: Add helpers for mux switching")
> Signed-off-by: Jernej Skrabec <[email protected]>

Reviewed-by: Chen-Yu Tsai <[email protected]>

Though I have a couple nits.
> ---
>  drivers/gpu/drm/sun4i/sun8i_tcon_top.c | 71 +++++++++++++++++++++-----
>  drivers/gpu/drm/sun4i/sun8i_tcon_top.h |  6 +++
>  2 files changed, 65 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
> index 8adda578c51b..9cbd655518b2 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
> +++ b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
> @@ -25,6 +25,49 @@ static bool sun8i_tcon_top_node_is_tcon_top(struct device_node *node)
>         return !!of_match_node(sun8i_tcon_top_of_table, node);
>  }
>
> +static unsigned int sun8i_tcon_top_get_tcon_map(struct device_node *node)
> +{
> +       static const u32 out_ports[] = {
> +               TCON_TOP_MIXER0_OUT_PORT,
> +               TCON_TOP_MIXER1_OUT_PORT,
> +       };
> +       unsigned int i, map = 0;
> +
> +       for (i = 0; i < ARRAY_SIZE(out_ports); i++) {

You can declare `i` directly in the for statement.

> +               struct device_node *port;
> +
> +               port = of_graph_get_port_by_id(node, out_ports[i]);

You could probably use the __free() cleanup macro and make `port`
scoped and put the reference automatically.

> +               if (!port)
> +                       continue;
> +
> +               for_each_of_graph_port_endpoint(port, ep) {
> +                       struct of_endpoint endpoint;
> +
> +                       if (of_graph_parse_endpoint(ep, &endpoint))
> +                               continue;
> +
> +                       if (endpoint.id < TCON_TOP_PORT_TCON_NUM)
> +                               map |= BIT(endpoint.id);
> +               }
> +
> +               of_node_put(port);

And this line wouldn't be needed.

> +       }
> +
> +       return map;
> +}
> +

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