linux-kernel - Re: [PATCH v4 24/24] drm/exynos: dsi: Adjust probe order

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Date:   Thu, 23 Sep 2021 10:14:28 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Sean Paul <sean@...rly.run>, freedreno@...ts.freedesktop.org,
        Kyungmin Park <kyungmin.park@...sung.com>,
        linux-kernel@...r.kernel.org,
        Xinliang Liu <xinliang.liu@...aro.org>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Tian Tao <tiantao6@...ilicon.com>,
        Inki Dae <inki.dae@...sung.com>,
        linux-samsung-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        dri-devel@...ts.freedesktop.org,
        John Stultz <john.stultz@...aro.org>,
        Chen Feng <puck.chen@...ilicon.com>,
        Xinwei Kong <kong.kongxinwei@...ilicon.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>
Subject: Re: [PATCH v4 24/24] drm/exynos: dsi: Adjust probe order

Hi Maxime,

On 22.09.2021 10:53, Maxime Ripard wrote:
> On Fri, Sep 17, 2021 at 02:35:05PM +0200, Marek Szyprowski wrote:
>> On 13.09.2021 12:30, Andrzej Hajda wrote:
>>> W dniu 10.09.2021 o 12:12, Maxime Ripard pisze:
>>>> Without proper care and an agreement between how DSI hosts and devices
>>>> drivers register their MIPI-DSI entities and potential components, we can
>>>> end up in a situation where the drivers can never probe.
>>>>
>>>> Most drivers were taking evasive maneuvers to try to workaround this,
>>>> but not all of them were following the same conventions, resulting in
>>>> various incompatibilities between DSI hosts and devices.
>>>>
>>>> Now that we have a sequence agreed upon and documented, let's convert
>>>> exynos to it.
>>>>
>>>> Signed-off-by: Maxime Ripard <maxime@...no.tech>
>>> This patch should be dropped, as it will probably break the driver.
>>>
>>> Exynos is already compatible with the pattern
>>> register-bus-then-get-sink, but it adds/removes panel/bridge
>>> dynamically, so it creates drm_device without waiting for downstream sink.
>> Right, this patch breaks Exynos DSI driver operation. Without it, the
>> whole series works fine on all Exynos based test boards.
> Thanks for testing. Did you have any board using one of those bridges in
> your test sample?

Nope, the only bridges I've tested are tc358764 and exynos-mic. However, 
both are used in a bit special way. The rest of my test boards just have 
a dsi panel.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland