Hi Stephen
On 5/10/2023 4:19 PM, Kuogee Hsieh wrote:
internal_hpd is referenced at both plug and unplug handle.
The majority purpose of mutext is try to serialize internal_hpd between
dp_bridge_hpd_disable() and either plug or unplug handle.
On 5/10/2023 4:11 PM, Abhinav Kumar wrote:
On 5/10/2023 3:46 PM, Stephen Boyd wrote:
Quoting Kuogee Hsieh (2023-05-10 13:31:05)
Intrenal_hpd is referenced by event thread but set by drm bridge
callback
context. Add mutex to protect internal_hpd to avoid conflicts between
threads.
Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
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This patch looks completely unnecessary. How can dp_bridge_hpd_enable()
be called at the same time that dp_bridge_hpd_disable() is called or
dp_bridge_hpd_notify() is called? Isn't there locking or ordering at a
higher layer?
Ack. We can drop this patch because we are protected by
bridge->hpd_mutex in drm_bridge_hpd_enable() / drm_bridge_hpd_disable
() and drm_bridge_hpd_notify().
I understood now, so what kuogee is referring to is that this
event_mutex protection is to not protect those 3 calls from each other
(since they are already protected as we saw above) but because
dp_hpd_plug_handle/dp_hpd_unplug_handle still uses
dp_display.internal_hpd to re-enable the hot-plug interrupt, this is
making sure that flow is protected as well.
