Hi Paul, Neil,
> Am 03.03.2022 um 18:20 schrieb Paul Cercueil <p...@crapouillou.net>:
>
> Hi Nikolaus,
>
> [snip]
>
>>> Well he said "the Ingenic DRM core" aka ingenic-drm-drv.c. You do have
>>> access to the main drm_device in the ingenic_drm_bind() function, so you
>>> can add it there (with a cleanup function calling
>>> drm_kms_helper_poll_fini() registered with drmm_add_action_or_reset()).
>> Well, do you really want to mix HPD detection between connector, Synopsys
>> bridge and Ingenic DRM core? These are independent...
>> Or should be accessed only through the bridge chain pointers.
>> IMHO we should keep separate functions separate.
>
> The drm_kms_helper_poll_init() just says "this DRM device may have connectors
> that need to be polled" so it very well fits inside the main driver, IMHO.
As far as I understand, it has the side-effect to always set
dev->mode_config.poll_enabled and
schedule_delayed_work() for all devices.
I am not sure if this is intended for arbitrary ingenic-drm devices. But you
know better than me.
Hm. But wait, I think I now finally remember why I have proposed it the way it
is!
It is always better to go back to requirements and find the least invasive
solution.
- HPD IRQ works and calls dw_hdmi_irq() [as can be shown by adding printk()]
- it is just that the udevd is only notified if poll_enabled = true (but no
polling takes place!).
An earlier version (v4) to fix this proposed to add an explicit call to
drm_kms_helper_hotplug_event()
in dw_hdmi_irq() but that was rejected a while ago because
drm_helper_hpd_irq_event() will already call it:
https://www.spinics.net/lists/dri-devel/msg316846.html
Since this did not take into account that dev->mode_config.poll_enabled must be
set true, I then proposed the
enable_poll() mechanism just to set this bit for the ingenic-dw-hdmi
specialization.
So a HPD event is delivered to the dw-hdmi driver as dw_hdmi_irq() and that
calls drm_helper_hpd_irq_event()
but not drm_kms_helper_hotplug_event() and user-space is not getting aware.
It is all a hack because we mix the dw-hdmi driver which originally did
register its own connector
with an explicit connector...
In summary I now thing that the v4 patch is the simplest and least invasive
solution.
We neither have to introduce a dw_hdmi_enable_poll() function or call
drm_kms_helper_poll_init() anywhere.
It is just a single line to add to dw-hdmi. And neither touches ingenic-dw-hdmi
nor ingenic-drm-drv.
So let's go back to v4 version (just modify commit message to better describe
why we have to call
drm_kms_helper_hotplug_event() explicitly) and forget about alternatives.
BR,
Nikolaus
