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SubjectRe: [PATCH v5] drm/msm/dp: Always clear mask bits to disable interrupts at dp_ctrl_reset_irq_ctrl()
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On 5/11/2022 6:03 PM, Dmitry Baryshkov wrote:
> On Thu, 12 May 2022 at 04:01, Stephen Boyd <swboyd@chromium.org> wrote:
>> Quoting Dmitry Baryshkov (2022-05-11 17:41:50)
>>> On 12/05/2022 03:02, Kuogee Hsieh wrote:
>>>> 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.
>> Agreed. I think the concern is that the event queue will have "stuff" in
>> it. If the event queue was all a threaded irq we could simply call
>> synchronize_irq() after disabling the irq bit in the DP hardware and
>> then we would know it is safe to power down the DP logic. Unfortunately
>> the event queue is a kthread so we can't do that and we have to rewrite
>> synchronize_irq() by checking that the event queue is empty and waiting
>> for it to empty out otherwise. It's not safe enough to simply do the
>> power operations underneath the event_lock because there's a queue in
>> the kthread that might be waiting to grab the event_lock to process.
> This sounds like a good reason to rewrite event_thread to use
> threaded_irq and/or workqueue.

ok, i will do

1) protect suspended flag with event_lock to prevent new event be added

2) disable interrupts

2) wait for event_q empty before turn off power

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