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Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to .detect() callback

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Hi Russell,


On 04-08-2016 15:31, Russell King - ARM Linux wrote:
> On Thu, Aug 04, 2016 at 02:58:00PM +0100, Jose Abreu wrote:
>> Hi Russell,
>>
>> I am not sure if this is a bug in DRM or a bad implementation of
>> dw-hdmi. I've seen at least two more drivers that do the edid
>> reading at the .detect() callback: nouveau and gma500. This is
>> noticeable if while sending video the edid changes like in a
>> compliance environment. In the environment that I tested I was
>> sending video and swapped an edid that had support for AI packets
>> to another one without support and I noticed that although the
>> hotplug is generated the edid was not being updated.
> The path should be:
>
> - HPD interrupt
> - drm_helper_hpd_irq_event()
>   - generates uevent to userspace
>   - output_poll_changed() called
>     - drm_fb_helper_hotplug_event()
>       - drm_fb_helper_probe_connector_modes()
>         - connector->fill_modes()
>           - drm_helper_probe_single_connector_modes()
>             - connector_funcs->get_modes()
>
> Now, if we don't have fbdev emulation, then things won't get much
> fruther than output_poll_changed(), and the responsibility for
> reading the EDID falls onto userspace.  However, as soon as userspace
> or the kernel reads the new EDID, that is when any changes in it
> should become visible.
>
> Of course, that should occur in a timely fashion.
>

Hmm, I am not debugging it right now but I remember that
drm_fb_helper_probe_connector_modes() was not being called at the
time I set the new EDID but only after I stopped sending video (I
was using modetest).


Best regards,
Jose Miguel Abreu

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[PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to .detect() callback Jose Abreu <Jose.Abreu@synopsys.com> - 2016-08-04 12:50 +0200
  Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-08-04 12:50 +0200
    Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Jose Abreu <Jose.Abreu@synopsys.com> - 2016-08-04 16:00 +0200
      Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-08-04 16:40 +0200
        Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Jose Abreu <Jose.Abreu@synopsys.com> - 2016-08-04 17:00 +0200
          Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-08-04 17:10 +0200
            Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Jose Abreu <Jose.Abreu@synopsys.com> - 2016-08-04 19:20 +0200
              Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Russell King - ARM Linux <linux@armlinux.org.uk> - 2016-08-05 01:20 +0200
                Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Daniel Vetter <daniel@ffwll.ch> - 2016-08-05 10:10 +0200
                Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Chris Wilson <chris@chris-wilson.co.uk> - 2016-08-05 10:20 +0200
                Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Jose Abreu <Jose.Abreu@synopsys.com> - 2016-08-08 18:30 +0200
                Re: [PATCH 3/3 v3] drm: bridge/dw-hdmi: Move edid reading to  .detect() callback Daniel Vetter <daniel@ffwll.ch> - 2016-08-09 08:10 +0200

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