[Intel-gfx] [PATCH v5 0/2] drm: Add detection of changing of edid on between suspend and resume

[Daniel Vetter]

On Thu, Apr 11, 2019 at 05:36:30PM +0300, Gwan-gyeong Mun wrote:
> This patch series fix missed detection of changing of edid on between
> suspend and resume.
> First patch fixes drm_helper_hdp_irq_event() in order to fix a below use
> case.
> 
>  Following scenario requires detection of changing of edid.
>     
>   1) plug display device to a connector
>   2) system suspend
>   3) unplug 1)'s display device and plug the other display device to a
>      connector
>   4) system resume
> 
> It adds edid check routine when a connector status still remains as
> "connector_status_connected".
> 
> Second patch adds a missed update of edid property of drm connector on i915.
>   
> v2: Add NULL check before comparing of EDIDs.
> v3: Make it as part of existing drm_helper_hpd_irq_event() (Stan, Mika)
> v4: Rebased
> v5: Use a cached edid property blob data of connector instead of adding
>     a new detected_edid variable. (Maarten)
>     Add an using of reference count for getting a cached edid property
>     blob data. (Maarten)
> 
> Testcase: igt/kms_chamelium/hdmi-edid-change-during-hibernate
> Testcase: igt/kms_chamelium/hdmi-edid-change-during-suspend
> Testcase: igt/kms_chamelium/dp-edid-change-during-hibernate
> Testcase: igt/kms_chamelium/dp-edid-change-during-suspend
> 
> v1, v2: https://patchwork.freedesktop.org/series/47680/
> v3: https://patchwork.freedesktop.org/series/49298/
> v4: https://patchwork.freedesktop.org/series/57397/

I guess I missed this, but there's a few fundamental things here first
imo:

- patch 2 is fallout from the fairly abitrary split between ->detect and
  ->get_modes. There's not really any good reason for that, I think we can
  just always call ->get_modes if ->detect says the connector is
  connected. There's more than just dp and hdmi (that's simply the 2
  things we test in CI using chamelium).

- the problem is bigger than just the edid changing (e.g. when repeaters
  change, or when something else changes aside from the edid, e.g. in dp
  aux, like how many lanes the dp cable has). Plus we have this long-term
  idea to give userspace a better idea about which connector exactly has
  changed. Therefor:

  1. add a new drm_connector->detect_epoque counter.
  2. Increment that counter every time something has changed, i.e. from
  probe helpers (we can push this down into the detect wrappers) when
  connector->status has changed, or when we update the edid blob.
  3. probe helpers look for changes in ->detect_epoque to decided whether
  to fire the uevent or not.
  4. long term we could expose the ->detect_epoque as a read-only
  property, or at least supply information about which connector caused
  the uevent using the new drm_sysfs_connector_status_event() (see the
  patch from Ram "[PATCH v3 09/10] drm: uevent for connector status
  change").

I think that gives us a much better long term foundation than adding lots
of hacks.

Cheers, Daniel

> 
> Gwan-gyeong Mun (2):
>   drm: Add detection of changing of edid on between suspend and resume
>   drm/i915: Add a missed update of edid property of drm connector
> 
>  drivers/gpu/drm/drm_probe_helper.c | 34 +++++++++++++++++++++++++++++-
>  drivers/gpu/drm/i915/intel_dp.c    |  1 +
>  drivers/gpu/drm/i915/intel_hdmi.c  |  1 +
>  3 files changed, 35 insertions(+), 1 deletion(-)
> 
> -- 
> 2.21.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch