linux-kernel - Re: [PATCH] drm/bridge: panel: Set orientation on panel

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Message-ID: <581da0b5-fcdf-aa02-cab8-3c0e65dd48f8@linaro.org>
Date:   Fri, 3 Feb 2023 09:08:07 +0100
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Doug Anderson <dianders@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     John Keeping <john@...anate.com>, Sam Ravnborg <sam@...nborg.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Robert Foss <rfoss@...nel.org>,
        Jonas Karlman <jonas@...boo.se>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Stephen Boyd <swboyd@...omium.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>
Subject: Re: [PATCH] drm/bridge: panel: Set orientation on panel_bridge
 connector

On 03/02/2023 01:45, Doug Anderson wrote:
> Hi,
> 
> On Mon, Jan 23, 2023 at 8:05 AM Laurent Pinchart
> <laurent.pinchart@...asonboard.com> wrote:
>>
>> Hi John,
>>
>> On Mon, Jan 23, 2023 at 12:16:45PM +0000, John Keeping wrote:
>>> On Sun, Jan 22, 2023 at 05:01:27PM +0200, Laurent Pinchart wrote:
>>>> On Sat, Jan 21, 2023 at 05:58:11PM +0000, John Keeping wrote:
>>>>> On Sat, Jan 21, 2023 at 09:57:18AM +0100, Sam Ravnborg wrote:
>>>>>> On Fri, Jan 20, 2023 at 01:44:38PM -0800, Doug Anderson wrote:
>>>>>>> On Fri, Jan 20, 2023 at 3:43 AM John Keeping wrote:
>>>>>>>>
>>>>>>>> Commit 15b9ca1641f0 ("drm: Config orientation property if panel provides
>>>>>>>> it") added a helper to set the panel panel orientation early but only
>>>>>>>> connected this for drm_bridge_connector, which constructs a panel bridge
>>>>>>>> with DRM_BRIDGE_ATTACH_NO_CONNECTOR and creates the connector itself.
>>>>>>>>
>>>>>>>> When the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is not specified and the
>>>>>>>> panel_bridge creates its own connector the orientation is not set unless
>>>>>>>> the panel does it in .get_modes which is too late and leads to a warning
>>>>>>>> splat from __drm_mode_object_add() because the device is already
>>>>>>>> registered.
>>>>>>>>
>>>>>>>> Call the necessary function to set add the orientation property when the
>>>>>>>> connector is created so that it is available before the device is
>>>>>>>> registered.
>>>>>>>
>>>>>>> I have no huge objection to your patch and it looks OK to me. That
>>>>>>> being said, my understanding is that:
>>>>>>>
>>>>>>> 1. DRM_BRIDGE_ATTACH_NO_CONNECTOR is "the future" and not using the
>>>>>>> flag is "deprecated".
>>>>>>
>>>>>> Correct.
>>>>>> Could we take a look at how much is required to move the relevant driver
>>>>>> to use DRM_BRIDGE_ATTACH_NO_CONNECTOR?
>>>>>>
>>>>>> If this is too much work now we may land this simple patch, but the
>>>>>> preference is to move all drivers to the new bridge handling and thus
>>>>>> asking display drivers to create the connector.
>>>>
>>>> I fully agree with Doug and Sam here. Let's see if we can keep the yak
>>>> shaving minimal :-)
>>>>
>>>>>> What display driver are we dealing with here?
>>>>>
>>>>> This is dw-mipi-dsi-rockchip which uses the component path in
>>>>> dw-mipi-dsi (and, in fact, is the only driver using that mode of
>>>>> dw-mipi-dsi).
>>>>>
>>>>> I'm not familiar enough with DRM to say whether it's easy to convert to
>>>>> DRM_BRIDGE_ATTACH_NO_CONNECTOR - should dw-mipi-dsi-rockchip be moving
>>>>> to use dw-mipi-dsi as a bridge driver or should dw_mipi_dsi_bind() have
>>>>> a drm_bridge_attach_flags argument?  But I'm happy to test patches if it
>>>>> looks easy to convert to you :-)
>>>>
>>>> I'd go for the former (use dw_mipi_dsi_probe() and acquire the DSI
>>>> bridge with of_drm_find_bridge() instead of using the component
>>>> framework) if possible, but I don't know how intrusive that would be.
>>>
>>> I'm a bit confused about what's required since dw-mipi-dsi-rockchip
>>> already uses dw_mipi_dsi_probe(),
>>
>> Indeed, my bad.
>>
>>> but I think moving away from the
>>> component framework would be significant work as that's how the MIPI
>>> subdriver fits in to the overall Rockchip display driver.
>>
>> It will be some work, yes. It however doesn't mean that the whole
>> Rockchip display driver needs to move away from the component framework,
>> it can be limited to the DSI encoder. It's not immediately clear to me
>> why the DSI encoder uses the component framework in the first place, and
>> if it would be difficult to move away from it.
>>
>>> Any changes / modernisation to the Rockchip MIPI driver look like it
>>> will take more time than I have available to spend on this, so I'd
>>> really like to see this patch land as it's a simple fix to an existing
>>> working code path.
>>
>> So who volunteers for fixing it properly ? :-)
>>
>> I'll let Doug and Sam decide regarding mering this patch.
> 
> This thread seems to have gone silent.
> 
> I'm inclined to merge this patch (removing the "Fixes" tag) since it's
> a one-line fix. While we want to encourage people to move to "the
> future", it seems like it would be better to wait until someone is
> trying to land something more intrusive than a 1-line fix before truly
> forcing the issue.
> 
> I'll plan to merge the patch to drm-misc-next early next week assuming
> there are no objections.

I'm ok for that,

Neil

> 
> -Doug