linux-kernel - Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received

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Message-ID: <64ad7053-beac-0c28-7d09-ea32a4f7fbad@quicinc.com>
Date:   Thu, 13 Jan 2022 12:44:16 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Stephen Boyd <swboyd@...omium.org>, <agross@...nel.org>,
        <airlied@...ux.ie>, <bjorn.andersson@...aro.org>,
        <daniel@...ll.ch>, <dmitry.baryshkov@...aro.org>,
        <dri-devel@...ts.freedesktop.org>, <robdclark@...il.com>,
        <sean@...rly.run>, <vkoul@...nel.org>
CC:     <quic_abhinavk@...cinc.com>, <aravindh@...eaurora.org>,
        <quic_sbillaka@...cinc.com>, <freedreno@...ts.freedesktop.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 1/4] drm/msm/dp: do not initialize phy until plugin
 interrupt received


On 1/13/2022 11:47 AM, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2022-01-13 09:51:42)
>> On 1/12/2022 8:13 PM, Stephen Boyd wrote:
>>>>>> -       if (dp->usbpd->orientation == ORIENTATION_CC2)
>>>>>> -               flip = true;
>>>>>> +       dp_power_init(dp->power, false);
>>>>>> +       dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
>>>>>> +
>>>>>> +       /*
>>>>>> +        * eDP is the embedded primary display and has its own phy
>>>>>> +        * initialize phy immediately
>>>>> Question still stands why we can't wait for hpd high from the eDP panel.
>>>>> Also, I think "has its own phy" means that it's not part of a combo
>>>>> USB+DP phy? Can you please clarify?
Correct, eDP has its dedicated phy which is not part of combo phy.
>>>>>> +        */
>>>>>> +       if (dp->dp_display.connector_type == DRM_MODE_CONNECTOR_eDP)
>>>>>> +               dp_display_host_phy_init(dp);
>>>>>>
>>>>>> -       dp_power_init(dp->power, flip);
>>>>>> -       dp_ctrl_host_init(dp->ctrl, flip, reset);
>>>>>>            dp_aux_init(dp->aux);
>>>>>>            dp->core_initialized = true;
>>>>>>     }
>>>>>> @@ -1306,20 +1330,23 @@ static int dp_pm_resume(struct device *dev)
>>>>>>            dp->hpd_state = ST_DISCONNECTED;
>>>>>>
>>>>>>            /* turn on dp ctrl/phy */
>>>>>> -       dp_display_host_init(dp, true);
>>>>>> +       dp_display_host_init(dp);
>>>>>>
>>>>>>            dp_catalog_ctrl_hpd_config(dp->catalog);
>>>>>>
>>>>>> -       /*
>>>>>> -        * set sink to normal operation mode -- D0
>>>>>> -        * before dpcd read
>>>>>> -        */
>>>>>> -       dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>>>>>>
>>>>>>            if (dp_catalog_link_is_connected(dp->catalog)) {
>>>>>> +               /*
>>>>>> +                * set sink to normal operation mode -- D0
>>>>>> +                * before dpcd read
>>>>>> +                */
>>>>>> +               dp_display_host_phy_init(dp);
>>>>>> +               dp_link_psm_config(dp->link, &dp->panel->link_info, false);
>>>>>>                    sink_count = drm_dp_read_sink_count(dp->aux);
>>>>>>                    if (sink_count < 0)
>>>>>>                            sink_count = 0;
>>>>>> +
>>>>>> +               dp_display_host_phy_exit(dp);
>>>>> Why is the phy exited on resume when the link is still connected? Is
>>>>> this supposed to be done only when the sink_count is 0? And how does
>>>>> this interact with eDP where the phy is initialized by the call to
>>>>> dp_display_host_init() earlier in this function.

At beginning of dp_pm_resume bot core_initialized and phy_initialized 
should be off.

However at the case of dongle still connected to DUT, we have to read 
dongle dpcd to decided any hdmi connect to dongle (sink_count != 0). in 
this case, we have to turn on phy to perform dpcd read and  turn off phy 
after read so the following plugged-in interrupt can be handled correctly.

>>>>>>            }
>>>>>>
>>>>>>            dp->link->sink_count = sink_count;
>>> Any response to the above two comments?
> ??