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From:   Chen-Yu Tsai <wens@csie.org>
Date:   Wed, 11 Jul 2018 11:11:56 +0800
Message-ID: <CAGb2v66vU4gBewGjLL-Ohx6mvKOVu4dDdwKNsXrkr3nZsSq3Cg@mail.gmail.com>
Subject: Re: [PATCH v2 10/18] drm/sun4i: mixer: Read id from DT
To:     Jernej Skrabec <jernej.skrabec@siol.net>
Cc:     Maxime Ripard <maxime.ripard@bootlin.com>,
        Rob Herring <robh+dt@kernel.org>,
        David Airlie <airlied@linux.ie>,
        Mark Rutland <mark.rutland@arm.com>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        devicetree <devicetree@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-sunxi <linux-sunxi@googlegroups.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Wed, Jul 11, 2018 at 4:35 AM, Jernej Skrabec <jernej.skrabec@siol.net> wrote:
> Currently, TCON supports 2 ways to match TCON with engine (mixer in this
> case). Old way is to just traverse of graph backwards and compare node
> pointer. New way is to match TCON and engine by their respective ids.
> All SoCs with DE2 enabled till now used the old way, which means mixer
> id was never used and thus never implemented.
>
> However, for R40, only the new way will be used. To prepare for that,
> implement mixer id fetching from DT.
>
> Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> ---
>  drivers/gpu/drm/sun4i/sun8i_mixer.c | 40 +++++++++++++++++++++++++++--
>  1 file changed, 38 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c b/drivers/gpu/drm/sun4i/sun8i_mixer.c
> index aa81b9838ae8..4bd4d8ccb34f 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
> +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
> @@ -22,6 +22,7 @@
>  #include <linux/component.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/of_device.h>
> +#include <linux/of_graph.h>
>  #include <linux/reset.h>
>
>  #include "sun4i_drv.h"
> @@ -322,6 +323,42 @@ static struct regmap_config sun8i_mixer_regmap_config = {
>         .max_register   = 0xbfffc, /* guessed */
>  };
>
> +static int sun8i_mixer_of_get_id(struct device_node *node)
> +{
> +       struct device_node *port, *ep;
> +       int ret = -EINVAL;
> +
> +       /* output is port 1 */
> +       port = of_graph_get_port_by_id(node, 1);
> +       if (!port)
> +               return -EINVAL;
> +
> +       /* try to find downstream endpoint */
> +       for_each_available_child_of_node(port, ep) {
> +               struct device_node *remote;
> +               u32 reg;
> +
> +               remote = of_graph_get_remote_endpoint(ep);
> +               if (!remote)
> +                       continue;
> +
> +               ret = of_property_read_u32(remote, "reg", &reg);
> +               if (!ret) {
> +                       of_node_put(remote);
> +                       of_node_put(ep);
> +                       of_node_put(port);
> +
> +                       return reg;
> +               }
> +
> +               of_node_put(remote);
> +       }
> +
> +       of_node_put(port);
> +
> +       return ret;
> +}
> +

The above looks good.

>  static int sun8i_mixer_bind(struct device *dev, struct device *master,
>                               void *data)
>  {
> @@ -353,8 +390,7 @@ static int sun8i_mixer_bind(struct device *dev, struct device *master,
>         dev_set_drvdata(dev, mixer);
>         mixer->engine.ops = &sun8i_engine_ops;
>         mixer->engine.node = dev->of_node;
> -       /* The ID of the mixer currently doesn't matter */
> -       mixer->engine.id = -1;
> +       mixer->engine.id = sun8i_mixer_of_get_id(dev->of_node);

Should you be handling error codes?

ChenYu