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

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Date:   Wed, 6 Jul 2022 20:57:06 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, 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 06/07/2022 20:54, Kuogee Hsieh wrote:
> 
> 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??

Yes.

> 
>>>> _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++;
>>>>
>>>>
>>
>>


-- 
With best wishes
Dmitry