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

[Maarten Lankhorst]

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

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.

~Maarten