linux-kernel - Re: [PATCH v1 2/2] drm/tegra: Use drm_dp_aux_register

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Date:   Tue, 9 Nov 2021 17:39:02 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Lyude Paul <lyude@...hat.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Thomas Graichen <thomas.graichen@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] drm/tegra: Use drm_dp_aux_register_ddc/chardev()
 helpers

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.
>