linux-kernel - Re: [PATCH v7] drm/msm/dp: Always clear mask bits to disable interrupts at dp_ctrl_reset_irq

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Date:   Fri, 20 May 2022 13:11:43 -0700
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,
        dianders@...omium.org, dmitry.baryshkov@...aro.org,
        robdclark@...il.com, sean@...rly.run, vkoul@...nel.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 v7] drm/msm/dp: Always clear mask bits to disable
 interrupts at dp_ctrl_reset_irq_ctrl()

Quoting Kuogee Hsieh (2022-05-17 09:21:34)
> 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.
>
> 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
>
> Changes in v6:
> -- add event_lock to protect "suspended"
>
> Changes in v7:
> -- delete "suspended" flag
>
> 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>