linux-kernel - Re: [PATCH v2] drm/bridge: adv7511: Attach to DSI host at probe time

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Date:   Thu, 29 Aug 2019 13:55:58 +0000
From:   Matt Redfearn <matt.redfearn@...nci.com>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        John Stultz <john.stultz@...aro.org>
CC:     Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Matthew Redfearn <matthew.redfearn@...nci.com>,
        Sean Paul <seanpaul@...omium.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v2] drm/bridge: adv7511: Attach to DSI host at probe time



On 28/08/2019 08:05, Andrzej Hajda wrote:
> On 27.08.2019 22:03, John Stultz wrote:
>> On Mon, Aug 19, 2019 at 3:27 PM John Stultz <john.stultz@...aro.org> wrote:
>>> On Thu, Jun 27, 2019 at 8:18 AM Matt Redfearn <matt.redfearn@...nci.com> wrote:
>>>> In contrast to all of the DSI panel drivers in drivers/gpu/drm/panel
>>>> which attach to the DSI host via mipi_dsi_attach() at probe time, the
>>>> ADV7533 bridge device does not. Instead it defers this to the point that
>>>> the upstream device connects to its bridge via drm_bridge_attach().
>>>> The generic Synopsys MIPI DSI host driver does not register it's own
>>>> drm_bridge until the MIPI DSI has attached. But it does not call
>>>> drm_bridge_attach() on the downstream device until the upstream device
>>>> has attached. This leads to a chicken and the egg failure and the DRM
>>>> pipeline does not complete.
>>>> Since all other mipi_dsi_device drivers call mipi_dsi_attach() in
>>>> probe(), make the adv7533 mipi_dsi_device do the same. This ensures that
>>>> the Synopsys MIPI DSI host registers it's bridge such that it is
>>>> available for the upstream device to connect to.
>>>>
>>>> Signed-off-by: Matt Redfearn <matt.redfearn@...nci.com>
>>>>
>>>> ---
>>> As a heads up, I just did some testing on drm-misc-next and this patch
>>> seems to be breaking the HiKey board.  On bootup, I'm seeing:
>>> [    4.209615] adv7511 2-0039: 2-0039 supply avdd not found, using
>>> dummy regulator
>>> [    4.217075] adv7511 2-0039: 2-0039 supply dvdd not found, using
>>> dummy regulator
>>> [    4.224453] adv7511 2-0039: 2-0039 supply pvdd not found, using
>>> dummy regulator
>>> [    4.231804] adv7511 2-0039: 2-0039 supply a2vdd not found, using
>>> dummy regulator
>>> [    4.239242] adv7511 2-0039: 2-0039 supply v3p3 not found, using
>>> dummy regulator
>>> [    4.246615] adv7511 2-0039: 2-0039 supply v1p2 not found, using
>>> dummy regulator
>>> [    4.272970] adv7511 2-0039: failed to find dsi host
>>>
>>> over and over.  The dummy regulator messages are normal, but usually
>>> [    4.444315] kirin-drm f4100000.ade: bound f4107800.dsi (ops dsi_ops)
>>>
>>> Starts up right afterward.
>> Hey Matt, Andrzej,
>>    I just wanted to follow up on this as this patch is breaking a
>> couple of boards. Any sense of what might be missing, or is this
>> something we should revert?
>>
>> I'm happy to test any patch ideas you have.
> 
> 
> I guess this is circular dependency issue:
> 
> - adv waits for dsi-host, then it creates drm_bridge,
> 
> - dsi-driver waits for drm_bridge, then it creates dsi host.
> 
> 
> The patch introduces proper order:
> 
> - 1st we should register devices buses,
> 
> - then we should wait for drm components.
> 
> 
> So the best solution would be to fix f4107800.dsi driver - it shouldn't
> look for drm_bridge in probe, instead it should register dsi_host, and
> in dsi host attach callback look for drm_bridge, then call component_add
> (if all required resources are gathered), see
> dw_mipi_dsi_rockchip_host_attach for example.

Hi all,

Sorry that my patch seems to have broken things. It was using the 
generic synopsys dsi driver 
(drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c) that I found the 
circular dependency fixed by my patch.

It appears that the patch has broken things for the platform specific 
synopsys dsi driver for Kirin. So another approach (though a lot more 
work) would be to switch Kirin over to using the generic synopsys dsi 
driver so that we have less redundancy in the tree.

Thanks,
Matt

> 
> 
> Regards
> 
> Andrzej
> 
> 
> 
>>
>> thanks
>> -john
>>
>>
>