linux-kernel - RE: [PATCH v9 2/4] drm/msm/dp: Support only IRQ

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Message-ID: <MW4PR02MB7186AE3B9B573FB1C594DA35E1F89@MW4PR02MB7186.namprd02.prod.outlook.com>
Date:   Mon, 25 Apr 2022 02:55:29 +0000
From:   "Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>
To:     Stephen Boyd <swboyd@...omium.org>,
        "Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "freedreno@...ts.freedesktop.org" <freedreno@...ts.freedesktop.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "robdclark@...il.com" <robdclark@...il.com>,
        "seanpaul@...omium.org" <seanpaul@...omium.org>,
        quic_kalyant <quic_kalyant@...cinc.com>,
        "Abhinav Kumar (QUIC)" <quic_abhinavk@...cinc.com>,
        "dianders@...omium.org" <dianders@...omium.org>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        "sean@...rly.run" <sean@...rly.run>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>,
        quic_vproddut <quic_vproddut@...cinc.com>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>,
        "steev@...i.org" <steev@...i.org>
Subject: RE: [PATCH v9 2/4] drm/msm/dp: Support only IRQ_HPD and REPLUG
 interrupts for eDP

Hi Stephen,

>Quoting Sankeerth Billakanti (2022-04-22 02:11:04)
>> The panel-edp enables the eDP panel power during probe, get_modes and
>> pre-enable. The eDP connect and disconnect interrupts for the eDP/DP
>> controller are directly dependent on panel power. As eDP display can
>> be assumed as always connected, the controller driver can skip the eDP
>> connect and disconnect interrupts. Any disruption in the link status
>> will be indicated via the IRQ_HPD interrupts.
>>
>> So, the eDP controller driver can just enable the IRQ_HPD and replug
>> interrupts. The DP controller driver still needs to enable all the
>> interrupts.
>>
>> Signed-off-by: Sankeerth Billakanti <quic_sbillaka@...cinc.com>
>
>The sprinkling of if conditions and manual driving of the DP plug/unplug state
>machine is pretty convoluted. To make it better the driver needs an overhaul.
>Anyway, it looks mostly fine to me except for this replug interrupt question
>below. Otherwise
>
>Reviewed-by: Stephen Boyd <swboyd@...omium.org>
>
>>  int dp_catalog_ctrl_get_interrupt(struct dp_catalog *dp_catalog) diff
>> --git a/drivers/gpu/drm/msm/dp/dp_display.c
>> b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 055681a..dea4de9 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -1096,6 +1097,13 @@ static void dp_display_config_hpd(struct
>dp_display_private *dp)
>>         dp_display_host_init(dp);
>>         dp_catalog_ctrl_hpd_config(dp->catalog);
>>
>> +       /* Enable plug and unplug interrupts only for external DisplayPort */
>> +       if (!dp->dp_display.is_edp)
>> +               dp_catalog_hpd_config_intr(dp->catalog,
>> +                               DP_DP_HPD_PLUG_INT_MASK |
>> +                               DP_DP_HPD_UNPLUG_INT_MASK,
>> +                               true);
>> +
>
>It seems like only the plug and unplug is enabled for DP here. Is replug
>enabled for eDP when it shouldn't be?
>

By default, all the interrupts are masked. This function is not executed for eDP
anymore because the host_init, phy_init and enable_irq are all done from
modeset_init for eDP with aux_bus. So, none of the eDP hpd interrupts are
enabled or unmasked before pre-enable.

The replug interrupt is unmasked for DP and eDP from the dp_hpd_plug_handle()
and masked from dp_hpd_unplug_handle().

>>         /* Enable interrupt first time
>>          * we are leaving dp clocks on during disconnect
>>          * and never disable interrupt