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

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Message-ID: <CAE-0n50YcX6sCoTR0bUy_GrZM7=UdHPAGYNwE3Nvj6GL4iTmMg@mail.gmail.com>
Date:   Wed, 27 Oct 2021 23:38:24 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     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
Cc:     robdclark@...il.com, seanpaul@...omium.org,
        kalyan_t@...eaurora.org, abhinavk@...eaurora.org,
        dianders@...omium.org, khsieh@...eaurora.org,
        mkrishn@...eaurora.org, sbillaka@...eaurora.org
Subject: Re: [PATCH v3 6/6] drm/msm/dp: Remove the hpd init delay for eDP

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?

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