Le ven., mars 4 2022 at 19:15:13 +0100, H. Nikolaus Schaller
<hns@xxxxxxxxxxxxx> a écrit :
Hi Paul,
Am 04.03.2022 um 19:04 schrieb Paul Cercueil <paul@xxxxxxxxxxxxxxx>:
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.
Ok, this is a case c).
I vaguely remember having tried to analyse what bridge->hpd_cb is but
stopped since it is 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().
Ah, ok, I see.
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.
Well, a little more analysis shows that
drm_bridge_connector_enable_hpd is called
in the *-drv.c for some other plaforms:
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/imx/dcss/dcss-dev.c#L292
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/imx/dcss/dcss-kms.c#L145
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/omapdrm/omap_drv.c#L393
https://elixir.bootlin.com/linux/v5.17-rc6/source/drivers/gpu/drm/msm/hdmi/hdmi.c#L317
So I think it should not be solved outside dw-hdmi.
Hm. Can we call drm_bridge_connector_enable_hpd() from inside dw-hdmi?
Or would this be the solution if merged? (I currently can't try code).
https://lore.kernel.org/lkml/a7d0b013-6114-07b3-0a7b-0d17db8a3982@xxxxxxxxxxxxxxxxxx/T/
Looks correct to me. It has been reviewed by two people so I believe it
will be merged very soon.
Cheers,
-Paul
