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From:   Xinliang Liu <xinliang.liu@linaro.org>
Date:   Wed, 8 Jul 2020 17:14:49 +0800
Message-ID: <CAKoKPbzjJa74b8kayVguLJF_PVzPD4jOfvnUJ-pr3HmytLiGAw@mail.gmail.com>
Subject: Re: [PATCH] drm/hisilicon/hibmc: Move drm_fbdev_generic_setup() down
 to avoid the splat
To:     Zenghui Yu <yuzenghui@huawei.com>
Cc:     dri-devel <dri-devel@lists.freedesktop.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Rongrong Zou <zourongrong@gmail.com>,
        John Stultz <john.stultz@linaro.org>,
        Xinwei Kong <kong.kongxinwei@hisilicon.com>,
        Chen Feng <puck.chen@hisilicon.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>, tzimmermann@suse.de,
        Sam Ravnborg <sam@ravnborg.org>, wanghaibin.wang@huawei.com
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Hi Zenghui,
Thanks for fixing this.
Applied to drm-misc-fixes.

Best,
-Xinliang

On Mon, 6 Jul 2020 at 22:53, Zenghui Yu <yuzenghui@huawei.com> wrote:
>
> The HiSilicon hibmc driver triggers a splat at boot time as below
>
> [   14.137806] ------------[ cut here ]------------
> [   14.142405] hibmc-drm 0000:0a:00.0: Device has not been registered.
> [   14.148661] WARNING: CPU: 0 PID: 496 at drivers/gpu/drm/drm_fb_helper.c:2233 drm_fbdev_generic_setup+0x15c/0x1b8
> [   14.158787] [...]
> [   14.278307] Call trace:
> [   14.280742]  drm_fbdev_generic_setup+0x15c/0x1b8
> [   14.285337]  hibmc_pci_probe+0x354/0x418
> [   14.289242]  local_pci_probe+0x44/0x98
> [   14.292974]  work_for_cpu_fn+0x20/0x30
> [   14.296708]  process_one_work+0x1c4/0x4e0
> [   14.300698]  worker_thread+0x2c8/0x528
> [   14.304431]  kthread+0x138/0x140
> [   14.307646]  ret_from_fork+0x10/0x18
> [   14.311205] ---[ end trace a2000ec2d838af4d ]---
>
> This turned out to be due to the fbdev device hasn't been registered when
> drm_fbdev_generic_setup() is invoked. Let's fix the splat by moving it down
> after drm_dev_register() which will follow the "Display driver example"
> documented by commit de99f0600a79 ("drm/drv: DOC: Add driver example
> code").
>
> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> ---
>  drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> index a6fd0c29e5b8..544b9993c99e 100644
> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
> @@ -307,8 +307,6 @@ static int hibmc_load(struct drm_device *dev)
>         /* reset all the states of crtc/plane/encoder/connector */
>         drm_mode_config_reset(dev);
>
> -       drm_fbdev_generic_setup(dev, dev->mode_config.preferred_depth);
> -
>         return 0;
>
>  err:
> @@ -355,6 +353,9 @@ static int hibmc_pci_probe(struct pci_dev *pdev,
>                           ret);
>                 goto err_unload;
>         }
> +
> +       drm_fbdev_generic_setup(dev, dev->mode_config.preferred_depth);
> +
>         return 0;
>
>  err_unload:
> --
> 2.19.1
>