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

[Mun, Gwan-gyeong]

On Mon, 2019-03-04 at 12:45 +0100, Maarten Lankhorst wrote:
> Op 01-03-2019 om 11:01 schreef Gwan-gyeong Mun:
> > The hotplug detection routine of drm_helper_hpd_irq_event() can
> > detect
> > changing of status of connector, but it can not detect changing of
> > edid.
> > 
> > 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".
> > 
> > v2: Add NULL check before comparing of EDIDs.
> > v3: Make it as part of existing drm_helper_hpd_irq_event() (Stan,
> > Mika)
> > 
> > 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
> > 
> > Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> > ---
> >  drivers/gpu/drm/drm_probe_helper.c | 29
> > ++++++++++++++++++++++++++++-
> >  1 file changed, 28 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c
> > b/drivers/gpu/drm/drm_probe_helper.c
> > index 6fd08e04b323..036a57d2b29e 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -742,7 +742,16 @@ EXPORT_SYMBOL(drm_kms_helper_poll_fini);
> >   * panels.
> >   *
> >   * This helper function is useful for drivers which can't or don't
> > track hotplug
> > - * interrupts for each connector.
> > + * interrupts for each connector. And it also supports a detection
> > of changing
> > + * of edid on between suspend and resume when a connector status
> > still remains
> > + * as "connector_status_connected".
> > + *
> > + * 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
> >   *
> >   * Drivers which support hotplug interrupts for each connector
> > individually and
> >   * which have a more fine-grained detect logic should bypass this
> > code and
> 
> We already have a drm_connector_update_edid_property(), so we cache
> edid already?
> 
> Could we use that, perhaps reworking slightly how edids are updated
> in i915?
> Like drm_connector_update_property_test
> 
Ok, I'll check a cached edid propery and will revise in order to use a
cached edid property.
> The current code feels like a hack. The fact we don't clear old_edid
> or free it, makes me worry that your current patch will either use
> old_edid after it'd freed, or have the old_edid leaked.
> 
You are right, I missed the case which you mentioned.
In the next patch, I'll handle an edid propery with
drm_property_blob_get() and drm_property_blob_put().
Thank you for checking.
Br,
G.G.
> ~Maarten
>