linux-kernel - Re: [PATCH v13 2/2] drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP

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Date:   Tue, 7 Jul 2020 15:01:25 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Xin Ji <xji@...logixsemi.com>
Cc:     devel@...verdev.osuosl.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Nicolas Boichat <drinkcat@...gle.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        lkml <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Pi-Hsun Shih <pihsun@...omium.org>,
        Shawn Ku <shawnku@...gle.com>,
        Sheng Pan <span@...logixsemi.com>
Subject: Re: [PATCH v13 2/2] drm/bridge: anx7625: Add anx7625 MIPI DSI/DPI to DP

On Tue, Jun 9, 2020 at 3:20 PM Xin Ji <xji@...logixsemi.com> wrote:
>
> The ANX7625 is an ultra-low power 4K Mobile HD Transmitter designed
> for portable device. It converts MIPI DSI/DPI to DisplayPort 1.3 4K.
>
> Signed-off-by: Xin Ji <xji@...logixsemi.com>
> ---
>  drivers/gpu/drm/bridge/analogix/Kconfig   |    9 +
>  drivers/gpu/drm/bridge/analogix/Makefile  |    1 +
>  drivers/gpu/drm/bridge/analogix/anx7625.c | 1999 +++++++++++++++++++++++++++++
>  drivers/gpu/drm/bridge/analogix/anx7625.h |  397 ++++++
>  4 files changed, 2406 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/analogix/anx7625.c
>  create mode 100644 drivers/gpu/drm/bridge/analogix/anx7625.h
>
> [snip]
> +static int anx7625_parse_dt(struct device *dev,
> +                           struct anx7625_platform_data *pdata)
> +{
> +       struct device_node *np = dev->of_node;
> +       struct device_node *panel_node, *out_ep;
> +
> +       pdata->node.mipi_dsi_host_node = of_graph_get_remote_node(np, 0, 0);
> +       if (!pdata->node.mipi_dsi_host_node) {
> +               DRM_DEV_ERROR(dev, "fail to get internal panel.\n");
> +               return -EPROBE_DEFER;

This does not look correct. I don't think of_graph_get_remote_node
will ever return NULL if the device tree is configured properly, and
it's useless to retry later (EPROBE_DEFER). You should just fail (e.g.
return EINVAL).

> +       }
> +
> +       of_node_put(pdata->node.mipi_dsi_host_node);

You are using pdata->node.mipi_dsi_host_node in other places in the
code, so I don't think it's ok to call of_node_put?

> +       DRM_DEV_DEBUG_DRIVER(dev, "found dsi host node.\n");
> +
> +       pdata->node.panel_node = of_graph_get_port_by_id(np, 1);
> +       if (!pdata->node.panel_node) {
> +               DRM_DEV_ERROR(dev, "fail to get panel node.\n");
> +               return -EPROBE_DEFER;

-EINVAL.

> +       }
> +
> +       of_node_put(pdata->node.panel_node);
> +       out_ep = of_get_child_by_name(pdata->node.panel_node,
> +                                     "endpoint");
> +       if (!out_ep) {
> +               DRM_DEV_DEBUG_DRIVER(dev, "cannot get endpoint.\n");

DRM_DEV_ERROR seems more appropriate

> +               return -EPROBE_DEFER;

-EINVAL

> +       }
> +
> +       panel_node = of_graph_get_remote_port_parent(out_ep);
> +       of_node_put(out_ep);
> +       pdata->panel = of_drm_find_panel(panel_node);
> +       DRM_DEV_DEBUG_DRIVER(dev, "get panel node.\n");
> +
> +       of_node_put(panel_node);
> +       if (IS_ERR_OR_NULL(pdata->panel))
> +               return -EPROBE_DEFER;

of_drm_find_panel cannot return NULL, so, do this instead:

if (IS_ERR(pdata->panel))
   return PTR_ERR(pdata->panel);

(which actually _may_ return EPROBE_DEFER)

> +
> +       return 0;
> +}
> [snip]
> +static int anx7625_i2c_probe(struct i2c_client *client,
> +                            const struct i2c_device_id *id)
> +{
> +       struct anx7625_data *platform;
> +       struct anx7625_platform_data *pdata;
> +       int ret = 0;
> +       struct device *dev = &client->dev;
> +
> +       if (!i2c_check_functionality(client->adapter,
> +                                    I2C_FUNC_SMBUS_I2C_BLOCK)) {
> +               DRM_DEV_ERROR(dev, "anx7625's i2c bus doesn't support\n");
> +               return -ENODEV;
> +       }
> +
> +       platform = kzalloc(sizeof(*platform), GFP_KERNEL);
> +       if (!platform) {
> +               DRM_DEV_ERROR(dev, "fail to allocate driver data\n");
> +               return -ENOMEM;
> +       }
> +
> +       pdata = &platform->pdata;
> +
> +       ret = anx7625_parse_dt(dev, pdata);
> +       if (ret) {
> +               DRM_DEV_ERROR(dev, "fail to parse devicetree.\n");

Please do not print this error (or at least not if err == -EPROBE_DEFER).

> +               goto free_platform;
> +       }