Re: [Letux-kernel] [PATCH v16 1/4] drm/bridge: dw-hdmi: introduce dw_hdmi_enable_poll()

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Le ven., mars 4 2022 at 18:51:14 +0100, H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> a écrit :
Hi Paul, Neil,

 Am 04.03.2022 um 17:47 schrieb Paul Cercueil <paul@xxxxxxxxxxxxxxx>:

From what I understood in Nikolaus' last message, HDMI hotplug is actually correctly detected, so there's no need for polling. What is missing is the call to drm_kms_helper_hotplug_event *somewhere*, so that the information is correctly relayed to userspace.

Exactly.

As Maxime pointed out it should already be called by drm_helper_hpd_irq_event() in dw_hdmi_irq() but isn't
because mode_config.poll_enabled isn't enabled.

So we can either
a) enable mode_config.poll_enabled so that it is called by drm_helper_hpd_irq_event() or

b) make drm_kms_helper_hotplug_event() being called explicitly in dw_hdmi_irq(). We could guard that by mode_config.poll_enabled to avoid drm_kms_helper_hotplug_event() being called twice (but I think the "changed" mechanism will take care of).

I think this issue can be fixed by calling drm_bridge_connector_enable_hpd() on the connector in ingenic-drm-drv.c.

I don't see yet how this would solve it, but it may work.

dw_hdmi_irq() calls drm_bridge_hpd_notify(), which would call bridge->hpd_cb() if it was non-NULL.

Calling drm_bridge_connector_enable_hpd() will set the bridge->hpd_cb() callback to point to drm_bridge_connector_hpd_cb(), which itself will call drm_kms_helper_hotplug_event(). Therefore, all that is missing is one call to drm_bridge_connector_enable_hpd().

Cheers,
-Paul


Anyways, this all is a missing feature (sometimes called "bug") of the *dw-hdmi driver* and IMHO
neither of the connector nor the ingenic-drm-drv.

So I think it should not be solved outside dw-hdmi.

BR and thanks,
Nikolaus







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