linux-kernel - Re: [PATCH v5] drm/msm/dp: Always clear mask bits to disable interrupts at dp_ctrl_reset_irq

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Date:   Thu, 12 May 2022 03:41:50 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, robdclark@...il.com,
        sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
        vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
        agross@...nel.org, bjorn.andersson@...aro.org
Cc:     quic_abhinavk@...cinc.com, quic_aravindh@...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 v5] drm/msm/dp: Always clear mask bits to disable
 interrupts at dp_ctrl_reset_irq_ctrl()

On 12/05/2022 03:02, Kuogee Hsieh wrote:
> dp_catalog_ctrl_reset() will software reset DP controller. But it will
> not reset programmable registers to default value. DP driver still have
> to clear mask bits to interrupt status registers to disable interrupts
> after software reset of controller.
> 
> At current implementation, dp_ctrl_reset_irq_ctrl() will software reset dp
> controller but did not call dp_catalog_ctrl_enable_irq(false) to clear hpd
> related interrupt mask bits to disable hpd related interrupts due to it
> mistakenly think hpd related interrupt mask bits will be cleared by software
> reset of dp controller automatically. This mistake may cause system to crash
> during suspending procedure due to unexpected irq fired and trigger event
> thread to access dp controller registers with controller clocks are disabled.
> 
> This patch fixes system crash during suspending problem by removing "enable"
> flag condition checking at dp_ctrl_reset_irq_ctrl() so that hpd related
> interrupt mask bits are cleared to prevent unexpected from happening.

ok. This is the main part of the description.

> In addition, this patch also add suspended flag to prevent new events be
> added into event Q to wake up event thread after system suspended.

And this describes the major part of the patch. First, it should go to a 
separate patch. Second, can you please describe, how can this happen 
once you disable the HPD interrupt?

> 
> Changes in v2:
> -- add more details commit text
> 
> Changes in v3:
> -- add synchrons_irq()
> -- add atomic_t suspended
> 
> Changes in v4:
> -- correct Fixes's commit ID
> -- remove synchrons_irq()
> 
> Changes in v5:
> -- revise commit text
> 
> Fixes: 989ebe7bc446 ("drm/msm/dp: do not initialize phy until plugin interrupt received")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_ctrl.c    |  9 +++++++--
>   drivers/gpu/drm/msm/dp/dp_display.c | 11 +++++++++++
>   2 files changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index af7a80c..f3e333e 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1389,8 +1389,13 @@ void dp_ctrl_reset_irq_ctrl(struct dp_ctrl *dp_ctrl, bool enable)
>   
>   	dp_catalog_ctrl_reset(ctrl->catalog);
>   
> -	if (enable)
> -		dp_catalog_ctrl_enable_irq(ctrl->catalog, enable);
> +	/*
> +	 * all dp controller programmable registers will not
> +	 * be reset to default value after DP_SW_RESET
> +	 * therefore interrupt mask bits have to be updated
> +	 * to enable/disable interrupts
> +	 */
> +	dp_catalog_ctrl_enable_irq(ctrl->catalog, enable);
>   }
>   
>   void dp_ctrl_phy_init(struct dp_ctrl *dp_ctrl)
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index c388323..79439b8 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -98,6 +98,8 @@ struct dp_display_private {
>   	struct dp_ctrl    *ctrl;
>   	struct dp_debug   *debug;
>   
> +	atomic_t suspended;

I think it'd be better to protect it with event_lock rather than using 
atomics.

> +
>   	struct dp_usbpd_cb usbpd_cb;
>   	struct dp_display_mode dp_mode;
>   	struct msm_dp dp_display;
> @@ -187,6 +189,11 @@ static int dp_add_event(struct dp_display_private *dp_priv, u32 event,
>   	int pndx;
>   
>   	spin_lock_irqsave(&dp_priv->event_lock, flag);
> +	if (atomic_read(&dp_priv->suspended)) {
> +		spin_unlock_irqrestore(&dp_priv->event_lock, flag);
> +		return -EPERM;
> +	}
> +
>   	pndx = dp_priv->event_pndx + 1;
>   	pndx %= DP_EVENT_Q_MAX;
>   	if (pndx == dp_priv->event_gndx) {
> @@ -1362,6 +1369,8 @@ static int dp_pm_resume(struct device *dev)
>   		dp->dp_display.connector_type, dp->core_initialized,
>   		dp->phy_initialized, dp_display->power_on);
>   
> +	atomic_set(&dp->suspended, 0);
> +
>   	/* start from disconnected state */
>   	dp->hpd_state = ST_DISCONNECTED;
>   
> @@ -1431,6 +1440,8 @@ static int dp_pm_suspend(struct device *dev)
>   		dp->dp_display.connector_type, dp->core_initialized,
>   		dp->phy_initialized, dp_display->power_on);
>   
> +	atomic_inc(&dp->suspended);
> +
>   	/* mainlink enabled */
>   	if (dp_power_clk_status(dp->power, DP_CTRL_PM))
>   		dp_ctrl_off_link_stream(dp->ctrl);


-- 
With best wishes
Dmitry