linux-kernel - Re: [PATCH v15 1/4] drm/msm/dp: do not initialize phy until plugin interrupt received

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Message-ID: <CAE-0n52UYBajrqGFqppun5oK82V3ppjvQxANU27kL95gCZtURg@mail.gmail.com>
Date:   Fri, 14 Jan 2022 15:41:44 -0600
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, 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 v15 1/4] drm/msm/dp: do not initialize phy until plugin
 interrupt received

Quoting Kuogee Hsieh (2022-01-14 13:11:47)
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 7cc4d21..7cd6222 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -696,12 +699,9 @@ static int dp_irq_hpd_handle(struct dp_display_private *dp, u32 data)
>          * dp core (ahb/aux clks) must be initialized before
>          * irq_hpd be handled
>          */
> -       if (dp->core_initialized) {
> -               ret = dp_display_usbpd_attention_cb(&dp->pdev->dev);
> -               if (ret == -ECONNRESET) { /* cable unplugged */
> -                       dp->core_initialized = false;
> -               }
> -       }
> +       if (dp->core_initialized)

When is this condition false? The irq isn't unmasked until the core has
been initialized. On the resume path I suppose the irq is enabled in
dp_display_host_init() calling dp_ctrl_reset_irq_ctrl(), and then we
could immediately get the interrupt but it will block on the event_mutex
lock.

> +               dp_display_usbpd_attention_cb(&dp->pdev->dev);
> +
>         DRM_DEBUG_DP("hpd_state=%d\n", state);
>
>         mutex_unlock(&dp->event_mutex);
> @@ -1363,14 +1373,16 @@ static int dp_pm_suspend(struct device *dev)
>                 if (dp_power_clk_status(dp->power, DP_CTRL_PM))
>                         dp_ctrl_off_link_stream(dp->ctrl);
>
> +               dp_display_host_phy_exit(dp);
> +
> +               /* host_init will be called at pm_resume */
>                 dp_display_host_deinit(dp);
> +       } else {
> +               dp_display_host_phy_exit(dp);

I fail to see where this condition happens. Can we suspend the device
without the irq being installed?

>         }
>
>         dp->hpd_state = ST_SUSPENDED;
>
> -       /* host_init will be called at pm_resume */
> -       dp->core_initialized = false;
> -
>         DRM_DEBUG_DP("After, core_inited=%d power_on=%d\n",
>                         dp->core_initialized, dp_display->power_on);
>