linux-kernel - Re: [PATCH v3 10/24] drm/sun4i: tcon: Generalize engine search algorithm

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Date:   Thu, 28 Jun 2018 10:06:52 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH v3 10/24] drm/sun4i: tcon: Generalize engine search algorithm

On Mon, Jun 25, 2018 at 8:02 PM, Jernej Skrabec <jernej.skrabec@...l.net> wrote:
> Current "old" method to find engine worked pretty well for DE2. However,
> it doesn't work when TCON TOP is between  mixer (engine) and TCON. TCON
> TOP has multiple input ports, but current engine search algorithm
> expects only one.
>
> This can be fixed by first looking for output port id and selecting
> matching input by subtracting 1 for the next round. This work even if
> there is only one input and output.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> ---
>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index 08747fc3ee71..264bcc43da11 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -791,12 +791,14 @@ static int sun4i_tcon_init_regmap(struct device *dev,
>   */
>  static struct sunxi_engine *
>  sun4i_tcon_find_engine_traverse(struct sun4i_drv *drv,
> -                               struct device_node *node)
> +                               struct device_node *node,
> +                               u32 port_id)
>  {
>         struct device_node *port, *ep, *remote;
>         struct sunxi_engine *engine = ERR_PTR(-EINVAL);
> +       u32 reg = 0;
>
> -       port = of_graph_get_port_by_id(node, 0);
> +       port = of_graph_get_port_by_id(node, port_id);
>         if (!port)
>                 return ERR_PTR(-EINVAL);
>
> @@ -826,8 +828,20 @@ sun4i_tcon_find_engine_traverse(struct sun4i_drv *drv,
>                 if (remote == engine->node)
>                         goto out_put_remote;
>
> +       /*
> +        * According to device tree binding input ports have even id
> +        * number and output ports have odd id. Since component with
> +        * more than one input and one output (TCON TOP) exits, correct
> +        * remote input id has to be calculated by subtracting 1 from
> +        * remote output id. If this for some reason can't be done, 0
> +        * is used as input port id.
> +        */

You need to call

    of_node_put(port);

to drop the reference to the original port.

Otherwise,

Reviewed-by: Chen-Yu Tsai <wens@...e.org>

> +       port = of_graph_get_remote_port(ep);
> +       if (!of_property_read_u32(port, "reg", &reg) && reg > 0)
> +               reg -= 1;
> +
>         /* keep looking through upstream ports */
> -       engine = sun4i_tcon_find_engine_traverse(drv, remote);
> +       engine = sun4i_tcon_find_engine_traverse(drv, remote, reg);
>
>  out_put_remote:
>         of_node_put(remote);
> @@ -950,7 +964,7 @@ static struct sunxi_engine *sun4i_tcon_find_engine(struct sun4i_drv *drv,
>
>         /* Fallback to old method by traversing input endpoints */
>         of_node_put(port);
> -       return sun4i_tcon_find_engine_traverse(drv, node);
> +       return sun4i_tcon_find_engine_traverse(drv, node, 0);
>  }
>
>  static int sun4i_tcon_bind(struct device *dev, struct device *master,
> --
> 2.18.0
>