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Subject: Re: [PATCH v1 2/2] drm/tegra: Use drm_dp_aux_register_ddc/chardev()
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From:   Dmitry Osipenko <digetx@gmail.com>
To:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Lyude Paul <lyude@redhat.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        Thomas Graichen <thomas.graichen@gmail.com>,
        dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Date:   Tue, 9 Nov 2021 17:39:02 +0300
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09.11.2021 17:17, Dmitry Osipenko пишет:
> 09.11.2021 17:08, Dmitry Osipenko пишет:
>>> +static void host1x_drm_dev_deinit(struct host1x_device *dev)
>>> +{
>>> +	struct drm_device *drm = dev_get_drvdata(&dev->dev);
>> And platform_unregister_drivers() should be moved here.
>>
> 
> Nah, that should cause deadlock. This ad-hoc is too lame.

Actually, there is no problem here as I see now. The host1x driver
populates DT nodes after host1x_register() [1], meaning that Host1x DRM
will be always inited first.

[1]
https://elixir.bootlin.com/linux/v5.15/source/drivers/gpu/host1x/dev.c#L475

Still I'm not a fan of the ad-hoc solution.

> Another solution is to defer probing of DP AUX driver while
> tegra_drm_device() returns NULL, but it's icky.
> 
> Reverting the original DP AUX DDC registration order is the best option
> so far, IMO.
>