linux-kernel - Re: [PATCH v2 04/12] drm/msm/dp: Move link training to atomic

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Message-ID: <4941c486-ccff-40bd-9b4b-9b84a0c028e4@oss.qualcomm.com>
Date: Fri, 8 Aug 2025 17:53:45 -0700
From: Jessica Zhang <jessica.zhang@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Dmitry Baryshkov
 <lumag@...nel.org>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Yongxing Mou <quic_yongmou@...cinc.com>
Subject: Re: [PATCH v2 04/12] drm/msm/dp: Move link training to
 atomic_enable()



On 8/8/2025 5:45 PM, Dmitry Baryshkov wrote:
> On 09/08/2025 03:35, Jessica Zhang wrote:
>> Currently, the DP link training is being done during HPD. Move
>> link training to atomic_enable() in accordance with the atomic_enable()
>> documentation.
>>
>> Link disabling is already done in atomic_post_disable() (as part of the
>> dp_ctrl_off_link_stream() helper).
>>
>> Finally, call the plug/unplug handlers directly in hpd_notify() instead
>> of queueing them in the event thread so that they aren't preempted by
>> other events.
> 
> This feels like two unrelated changes.

Hi Dmitry,

Ack. Would it make more sense to squash the hpd_notify part with the IRQ 
thread change?

Thanks,

Jessica Zhang

> 
>>
>> Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
>> ---
>>   drivers/gpu/drm/msm/dp/dp_display.c | 15 ++++++++-------
>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/ 
>> msm/dp/dp_display.c
>> index e2556de99894..c849befe58f0 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -427,11 +427,6 @@ static int msm_dp_display_process_hpd_high(struct 
>> msm_dp_display_private *dp)
>>       msm_dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>>       msm_dp_link_reset_phy_params_vx_px(dp->link);
>> -    rc = msm_dp_ctrl_on_link(dp->ctrl);
>> -    if (rc) {
>> -        DRM_ERROR("failed to complete DP link training\n");
>> -        goto end;
>> -    }
>>       msm_dp_add_event(dp, EV_USER_NOTIFICATION, true, 0);
>> @@ -1680,6 +1675,12 @@ void msm_dp_bridge_atomic_enable(struct 
>> drm_bridge *drm_bridge,
>>           force_link_train = true;
>>       }
>> +    rc = msm_dp_ctrl_on_link(msm_dp_display->ctrl);
>> +    if (rc) {
>> +        DRM_ERROR("Failed link training (rc=%d)\n", rc);
>> +        dp->connector->state->link_status = DRM_LINK_STATUS_BAD;
>> +    }
>> +
>>       msm_dp_display_enable(msm_dp_display, force_link_train);
>>       rc = msm_dp_display_post_enable(dp);
>> @@ -1839,7 +1840,7 @@ void msm_dp_bridge_hpd_notify(struct drm_bridge 
>> *bridge,
>>           return;
>>       if (!msm_dp_display->link_ready && status == 
>> connector_status_connected)
>> -        msm_dp_add_event(dp, EV_HPD_PLUG_INT, 0, 0);
>> +        msm_dp_hpd_plug_handle(dp, 0);
>>       else if (msm_dp_display->link_ready && status == 
>> connector_status_disconnected)
>> -        msm_dp_add_event(dp, EV_HPD_UNPLUG_INT, 0, 0);
>> +        msm_dp_hpd_unplug_handle(dp, 0);
>>   }
>>
> 
>