linux-kernel - Re: [PATCH v3] drm/msm/dp: check core_initialized flag at both host_init() and host

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Message-ID: <CAA8EJpquZAhn+HswNxardN1fE8Zu1CKrCU5EiX=B8mGWuxfWnQ@mail.gmail.com>
Date:   Wed, 1 Mar 2023 04:16:12 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        dianders@...omium.org, vkoul@...nel.org, daniel@...ll.ch,
        airlied@...il.com, agross@...nel.org, andersson@...nel.org,
        quic_abhinavk@...cinc.com, quic_sbillaka@...cinc.com,
        freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drm/msm/dp: check core_initialized flag at both
 host_init() and host_deinit()

On Wed, 1 Mar 2023 at 02:17, Kuogee Hsieh <quic_khsieh@...cinc.com> wrote:
>
> There is a reboot/suspend test case where system suspend is forced
> during system booting up. Since dp_display_host_init() of external
> DP is executed at hpd thread context, this test case may created a
> scenario that dp_display_host_deinit() from pm_suspend() run before
> dp_display_host_init() if hpd thread has no chance to run during
> booting up while suspend request command was issued. At this scenario
> system will crash at aux register access at dp_display_host_deinit()
> since aux clock had not yet been enabled by dp_display_host_init().
> Therefore we have to ensure aux clock enabled by checking
> core_initialized flag before access aux registers at pm_suspend.

Can a call to dp_display_host_init() be moved from
dp_display_config_hpd() to dp_display_bind()?

Related question: what is the primary reason for having
EV_HPD_INIT_SETUP and calling dp_display_config_hpd() via the event
thread? Does DP driver really depend on DPU irqs being installed? As
far as I understand, DP device uses MDSS interrupts and those IRQs are
available and working at the time of dp_display_probe() /
dp_display_bind().

>
> Changes in v2:
> -- at commit text, dp_display_host_init() instead of host_init()
> -- at commit text, dp_display_host_deinit() instead of host_deinit()
>
> Changes in v3:
> -- re arrange to avoid commit text line over 75 chars
>
> Fixes: 989ebe7bc446 ("drm/msm/dp: do not initialize phy until plugin interrupt received")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_display.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index bde1a7c..1850738 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -460,10 +460,12 @@ static void dp_display_host_init(struct dp_display_private *dp)
>                 dp->dp_display.connector_type, dp->core_initialized,
>                 dp->phy_initialized);
>
> -       dp_power_init(dp->power, false);
> -       dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
> -       dp_aux_init(dp->aux);
> -       dp->core_initialized = true;
> +       if (!dp->core_initialized) {
> +               dp_power_init(dp->power, false);
> +               dp_ctrl_reset_irq_ctrl(dp->ctrl, true);
> +               dp_aux_init(dp->aux);
> +               dp->core_initialized = true;
> +       }
>  }
>
>  static void dp_display_host_deinit(struct dp_display_private *dp)
> @@ -472,10 +474,12 @@ static void dp_display_host_deinit(struct dp_display_private *dp)
>                 dp->dp_display.connector_type, dp->core_initialized,
>                 dp->phy_initialized);
>
> -       dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
> -       dp_aux_deinit(dp->aux);
> -       dp_power_deinit(dp->power);
> -       dp->core_initialized = false;
> +       if (dp->core_initialized) {
> +               dp_ctrl_reset_irq_ctrl(dp->ctrl, false);
> +               dp_aux_deinit(dp->aux);
> +               dp_power_deinit(dp->power);
> +               dp->core_initialized = false;
> +       }
>  }
>
>  static int dp_display_usbpd_configure_cb(struct device *dev)
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>


-- 
With best wishes
Dmitry