linux-kernel - Re: [PATCH v3 6/6] drm/msm/dp: Remove the hpd init delay for eDP

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Message-ID: <d04f4082266e599cbba458d5e39e75e9@codeaurora.org>
Date:   Fri, 29 Oct 2021 10:20:28 -0700
From:   khsieh@...eaurora.org
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        robdclark@...il.com, seanpaul@...omium.org,
        kalyan_t@...eaurora.org, abhinavk@...eaurora.org,
        dianders@...omium.org, mkrishn@...eaurora.org,
        sbillaka@...eaurora.org
Subject: Re: [PATCH v3 6/6] drm/msm/dp: Remove the hpd init delay for eDP

On 2021-10-27 23:38, Stephen Boyd wrote:
> Quoting Sankeerth Billakanti (2021-10-27 18:54:48)
>> DP driver needs a 10 second delay before phy_init so that
>> the usb combo phy initializes and sets up the necessary
>> clocks for usb devices such as keyboard and mouse.
>> 
>> eDP controller uses a standalone phy and need not wait for
>> phy initialization from any other component. This change
>> will remove the delay for eDP controller.
>> 
>> Signed-off-by: Sankeerth Billakanti <quic_sbillaka@...cinc.com>
>> ---
>>  drivers/gpu/drm/msm/dp/dp_display.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c 
>> b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 61385d6..de6a1fd 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -1438,7 +1439,15 @@ void msm_dp_irq_postinstall(struct msm_dp 
>> *dp_display)
>> 
>>         dp_hpd_event_setup(dp);
>> 
>> -       dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
>> +       if (dp->dp_display.connector_type == DRM_MODE_CONNECTOR_eDP) {
>> +               /* eDP does not need any delay before phy init */
>> +               delay = 0;
>> +       } else {
>> +               /* DP needs 10 second delay to let usb combo phy 
>> initialize */
> 
> This seems to be a different approach to the patch Kuogee sent a week 
> or
> two ago. Can we figure out what's wrong with the DP phy starting before
> the USB phy? I suppose this patch is OK as a temporary hack to keep
> moving with eDP, but we really need to figure out what's wrong with DP
> so this delay can be removed entirely. Has any progress been made on
> that?
> 
Sankeerth,
Can you drop this patch for now.
Let's discuss more.

>> +               delay = 100;
>> +       }
>> +
>> +       dp_add_event(dp, EV_HPD_INIT_SETUP, 0, delay);