linux-kernel - Re: [PATCH v3] drm/msm/dp: make eDP panel as the first connected connector

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Message-ID: <cdbfbad1-83a3-b15d-3000-eec425ae140c@quicinc.com>
Date:   Wed, 6 Jul 2022 10:54:19 -0700
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        <robdclark@...il.com>, <sean@...rly.run>, <swboyd@...omium.org>,
        <dianders@...omium.org>, <vkoul@...nel.org>, <daniel@...ll.ch>,
        <airlied@...ux.ie>, <agross@...nel.org>,
        <bjorn.andersson@...aro.org>
CC:     <quic_abhinavk@...cinc.com>, <quic_aravindh@...cinc.com>,
        <quic_sbillaka@...cinc.com>, <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] drm/msm/dp: make eDP panel as the first connected
 connector


On 7/6/2022 10:41 AM, Dmitry Baryshkov wrote:
> On 06/07/2022 20:38, Kuogee Hsieh wrote:
>>
>> On 7/6/2022 10:25 AM, Dmitry Baryshkov wrote:
>>> On 06/07/2022 20:24, Kuogee Hsieh wrote:
>>>> Some userspace presumes that the first connected connector is the main
>>>> display, where it's supposed to display e.g. the login screen. For
>>>> laptops, this should be the main panel.
>>>>
>>>> This patch call drm_helper_move_panel_connectors_to_head() after
>>>> drm_bridge_connector_init() to make sure eDP stay at head of
>>>> connected connector list. This fixes unexpected corruption happen
>>>> at eDP panel if eDP is not placed at head of connected connector
>>>> list.
>>>>
>>>> Changes in v2:
>>>> -- move drm_helper_move_panel_connectors_to_head() to
>>>>         dpu_kms_drm_obj_init()
>>>>
>>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
>>>> ---
>>>>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 2 ++
>>>>   1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c 
>>>> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>>> index 2b9d931..50ff666 100644
>>>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
>>>> @@ -763,6 +763,8 @@ static int _dpu_kms_drm_obj_init(struct dpu_kms 
>>>> *dpu_kms)
>>>>       if (ret)
>>>>           return ret;
>>>>   +    drm_helper_move_panel_connectors_to_head(dev);
>>>
>>> This should be in msm_drv.c unless you have a strong reason to have 
>>> it here.
>> Can you please  provide more info why should be in msm_drv.c?
>
> Let me quote my message from v1 review:
>
> Please move this call to the msm_drm_init(). Calling this function 
> somewhere after the ->kms_init() would make sure that all panel 
> connectors are close to the top of the list, whichever MDP/DPU driver 
> is used and whichever actual interface is bound to this panel.
>
Below are the call flow in timing order, ->kms_init does not create 
connectors/interfaces, hw_init does that.

1) ->kms_init

2) ->hw_init -> dpu_kms_hw_init --> _dpu_kms_drm_obj_init()  --> 
_dpu_kms_setup_displays()--> msm_dp_modeset_init() --> creator 
connectors/interfaces

3) drm_helper_move_panel_connectors_to_head() <== add here??

>>> _dpu_kms_drm_obj_init() create and initialize drm obj one by one and 
>>> _dpu_kms_setup_displays() had created system wide 
>>> connectors/interfaces .
>>
>> After that should be fine to move edp to head of connector list.
>>
>>>> +
>>>>       num_encoders = 0;
>>>>       drm_for_each_encoder(encoder, dev)
>>>>           num_encoders++;
>>>
>>>
>
>