Re: [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@xxxxxxxxxxxx> 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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