linux-kernel - Re: [PATCH v2 7/7] drm/msm/dp: retrain link when loss of symbol lock detected

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Message-ID: <CAE-0n525b3V9D+aT_xwHQK-g6SjAXse4j7f1wHQHzeL3EEFV_w@mail.gmail.com>
Date:   Thu, 22 Jul 2021 19:14:21 +0000
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>,
        dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run
Cc:     abhinavk@...eaurora.org, aravindh@...eaurora.org, airlied@...ux.ie,
        daniel@...ll.ch, bjorn.andersson@...aro.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] drm/msm/dp: retrain link when loss of symbol lock detected

Quoting Kuogee Hsieh (2021-07-13 08:54:07)
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 6a013b0..20951c8 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1638,6 +1638,25 @@ static bool dp_ctrl_clock_recovery_any_ok(
>         return drm_dp_clock_recovery_ok(link_status, lane_count);
>  }
>
> +static bool dp_ctrl_loss_symbol_lock(struct dp_ctrl_private *ctrl)
> +{
> +       u8 link_status[DP_LINK_STATUS_SIZE];
> +       u8 status;
> +       int i;
> +       int num_lanes = ctrl->link->link_params.num_lanes;
> +
> +       dp_ctrl_read_link_status(ctrl, link_status);
> +
> +       for (i = 0; i < num_lanes; i++) {
> +               status = link_status[i / 2];
> +               status >>= ((i % 2) * 4);
> +               if (!(status & DP_LANE_SYMBOL_LOCKED))
> +                       return true;
> +       }
> +
> +       return false;
> +}

Can this function move to drivers/gpu/drm/drm_dp_helper.c and be called
drm_dp_symbol_locked()?

> +
>  int dp_ctrl_on_link(struct dp_ctrl *dp_ctrl)
>  {
>         int rc = 0;