Date:   Thu, 9 Dec 2021 14:29:30 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Guillaume Ranquet <granquet@...libre.com>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Markus Schneider-Pargmann <msp@...libre.com>,
        kernel test robot <lkp@...el.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 7/7] drm/mediatek: Add mt8195 DisplayPort driver

On Wed, Nov 10, 2021 at 9:08 PM Guillaume Ranquet <granquet@...libre.com> wrote:
>
> From: Markus Schneider-Pargmann <msp@...libre.com>
>
> This patch adds a DisplayPort driver for the Mediatek mt8195 SoC and a
> according phy driver mediatek-dp-phy.
>
> It supports both functional units on the mt8195, the embedded
> DisplayPort as well as the external DisplayPort units. It offers
> hot-plug-detection, audio up to 8 channels, and DisplayPort 1.4 with up
> to 4 lanes.
>
> The driver creates a child device for the phy. The child device will
> never exist without the parent being active. As they are sharing a
> register range, the parent passes a regmap pointer to the child so that
> both can work with the same register range. The phy driver sets device
> data that is read by the parent to get the phy device that can be used
> to control the phy properties.
>
> This driver is based on an initial version by
> Jason-JH.Lin <jason-jh.lin@...iatek.com>.
>
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> Reported-by: kernel test robot <lkp@...el.com>
> ---


<snip>

> +static int mtk_dp_probe(struct platform_device *pdev)
> +{
> +       struct mtk_dp *mtk_dp;
> +       struct device *dev = &pdev->dev;
> +       int ret;
> +       int irq_num = 0;
> +       struct drm_panel *panel = NULL;
> +
> +       mtk_dp = devm_kzalloc(dev, sizeof(*mtk_dp), GFP_KERNEL);
> +       if (!mtk_dp)
> +               return -ENOMEM;
> +
> +       mtk_dp->dev = dev;
> +
> +       irq_num = platform_get_irq(pdev, 0);
> +       if (irq_num < 0) {
> +               dev_err(dev, "failed to request dp irq resource\n");
> +               return -EPROBE_DEFER;
> +       }
> +
> +       ret = drm_of_find_panel_or_bridge(dev->of_node, 1, 0, &panel,
> +                                         &mtk_dp->next_bridge);
> +       if (ret == -ENODEV) {
> +               dev_info(
> +                       dev,
> +                       "No panel connected in devicetree, continuing as external DP\n");
> +               mtk_dp->next_bridge = NULL;
> +       } else if (ret) {
> +               dev_err(dev, "Failed to find panel or bridge: %d\n", ret);

Hi,

We're seeing
[    0.424599] mediatek-drm-dp 1c500000.edp_tx: Failed to find panel
or bridge: -517

It's probably better to use dev_err_probe here.

Thanks

> +               return ret;
> +       }
> +
> +       if (panel) {
> +               mtk_dp->next_bridge = devm_drm_panel_bridge_add(dev, panel);
> +               if (IS_ERR(mtk_dp->next_bridge)) {
> +                       ret = PTR_ERR(mtk_dp->next_bridge);
> +                       dev_err(dev, "Failed to create bridge: %d\n", ret);
> +                       return -EPROBE_DEFER;
> +               }
> +       }


<snip>

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