Re: [PATCH v2] drm/radeon: Retry DDC probing on DVI on failure if we got an HPD interrupt

["Christian König" <christian.koenig@amd.com>]

On 04.12.2015 00:26, cpaul@redhat.com wrote:
> From: Lyude <cpaul@redhat.com>
>
> HPD signals on DVI ports can be fired off before the pins required for
> DDC probing actually make contact, due to the pins for HPD making
> contact first. This results in a HPD signal being asserted but DDC
> probing failing, resulting in hotplugging occasionally failing.
>
> This is somewhat rare on most cards (depending on what angle you plug
> the DVI connector in), but on some cards it happens constantly. The
> Radeon R5 on the machine used for testing this patch for instance, runs
> into this issue just about every time I try to hotplug a DVI monitor and
> as a result hotplugging almost never works.
>
> Rescheduling the hotplug work for a second when we run into an HPD
> signal with a failing DDC probe usually gives enough time for the rest
> of the connector's pins to make contact, and fixes this issue.
>
> Signed-off-by: Lyude <cpaul@redhat.com>

I find a second a bit long, but if it works so what?

Looks sane enough to me, patch is Reviewed-by: Christian König 
<christian.koenig@amd.com>

> ---
> Sending this version of the patch because Jerome says this will probably be the
> least controversial of the potential fixes. Instead of sending userspace tons of
> hotplug events, we just reschedule the hotplug work.
>
>   drivers/gpu/drm/radeon/cik.c               |  2 +-
>   drivers/gpu/drm/radeon/evergreen.c         |  2 +-
>   drivers/gpu/drm/radeon/r100.c              |  2 +-
>   drivers/gpu/drm/radeon/r600.c              |  2 +-
>   drivers/gpu/drm/radeon/radeon.h            |  2 +-
>   drivers/gpu/drm/radeon/radeon_connectors.c | 21 ++++++++++++++++++++-
>   drivers/gpu/drm/radeon/radeon_irq_kms.c    |  8 ++++----
>   drivers/gpu/drm/radeon/radeon_mode.h       |  1 +
>   drivers/gpu/drm/radeon/rs600.c             |  2 +-
>   drivers/gpu/drm/radeon/si.c                |  2 +-
>   10 files changed, 32 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/radeon/cik.c b/drivers/gpu/drm/radeon/cik.c
> index 248953d..6801a0c 100644
> --- a/drivers/gpu/drm/radeon/cik.c
> +++ b/drivers/gpu/drm/radeon/cik.c
> @@ -8472,7 +8472,7 @@ restart_ih:
>   	if (queue_dp)
>   		schedule_work(&rdev->dp_work);
>   	if (queue_hotplug)
> -		schedule_work(&rdev->hotplug_work);
> +		schedule_delayed_work(&rdev->hotplug_work, 0);
>   	if (queue_reset) {
>   		rdev->needs_reset = true;
>   		wake_up_all(&rdev->fence_queue);
> diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
> index 0acde19..f8e4986 100644
> --- a/drivers/gpu/drm/radeon/evergreen.c
> +++ b/drivers/gpu/drm/radeon/evergreen.c
> @@ -5368,7 +5368,7 @@ restart_ih:
>   	if (queue_dp)
>   		schedule_work(&rdev->dp_work);
>   	if (queue_hotplug)
> -		schedule_work(&rdev->hotplug_work);
> +		schedule_delayed_work(&rdev->hotplug_work, 0);
>   	if (queue_hdmi)
>   		schedule_work(&rdev->audio_work);
>   	if (queue_thermal && rdev->pm.dpm_enabled)
> diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100.c
> index 238b13f..2df3c86 100644
> --- a/drivers/gpu/drm/radeon/r100.c
> +++ b/drivers/gpu/drm/radeon/r100.c
> @@ -806,7 +806,7 @@ int r100_irq_process(struct radeon_device *rdev)
>   		status = r100_irq_ack(rdev);
>   	}
>   	if (queue_hotplug)
> -		schedule_work(&rdev->hotplug_work);
> +		schedule_delayed_work(&rdev->hotplug_work, 0);
>   	if (rdev->msi_enabled) {
>   		switch (rdev->family) {
>   		case CHIP_RS400:
> diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c
> index 4ea5b10..cc2fdf0 100644
> --- a/drivers/gpu/drm/radeon/r600.c
> +++ b/drivers/gpu/drm/radeon/r600.c
> @@ -4276,7 +4276,7 @@ restart_ih:
>   		WREG32(IH_RB_RPTR, rptr);
>   	}
>   	if (queue_hotplug)
> -		schedule_work(&rdev->hotplug_work);
> +		schedule_delayed_work(&rdev->hotplug_work, 0);
>   	if (queue_hdmi)
>   		schedule_work(&rdev->audio_work);
>   	if (queue_thermal && rdev->pm.dpm_enabled)
> diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
> index b6cbd81..87db649 100644
> --- a/drivers/gpu/drm/radeon/radeon.h
> +++ b/drivers/gpu/drm/radeon/radeon.h
> @@ -2414,7 +2414,7 @@ struct radeon_device {
>   	struct r600_ih ih; /* r6/700 interrupt ring */
>   	struct radeon_rlc rlc;
>   	struct radeon_mec mec;
> -	struct work_struct hotplug_work;
> +	struct delayed_work hotplug_work;
>   	struct work_struct dp_work;
>   	struct work_struct audio_work;
>   	int num_crtc; /* number of crtcs */
> diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
> index 5a2cafb..340f3f5 100644
> --- a/drivers/gpu/drm/radeon/radeon_connectors.c
> +++ b/drivers/gpu/drm/radeon/radeon_connectors.c
> @@ -1234,13 +1234,32 @@ radeon_dvi_detect(struct drm_connector *connector, bool force)
>   	if (r < 0)
>   		return connector_status_disconnected;
>   
> +	if (radeon_connector->detected_hpd_without_ddc) {
> +		force = true;
> +		radeon_connector->detected_hpd_without_ddc = false;
> +	}
> +
>   	if (!force && radeon_check_hpd_status_unchanged(connector)) {
>   		ret = connector->status;
>   		goto exit;
>   	}
>   
> -	if (radeon_connector->ddc_bus)
> +	if (radeon_connector->ddc_bus) {
>   		dret = radeon_ddc_probe(radeon_connector, false);
> +
> +		/* Sometimes the pins required for the DDC probe on DVI
> +		 * connectors don't make contact at the same time that the ones
> +		 * for HPD do. If the DDC probe fails even though we had an HPD
> +		 * signal, try again later */
> +		if (!dret && !force &&
> +		    connector->status != connector_status_connected) {
> +			DRM_DEBUG_KMS("hpd detected without ddc, retrying in 1 second\n");
> +			radeon_connector->detected_hpd_without_ddc = true;
> +			schedule_delayed_work(&rdev->hotplug_work,
> +					      msecs_to_jiffies(1000));
> +			goto exit;
> +		}
> +	}
>   	if (dret) {
>   		radeon_connector->detected_by_load = false;
>   		radeon_connector_free_edid(connector);
> diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c
> index 171d3e4..979f3bf 100644
> --- a/drivers/gpu/drm/radeon/radeon_irq_kms.c
> +++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c
> @@ -74,7 +74,7 @@ irqreturn_t radeon_driver_irq_handler_kms(int irq, void *arg)
>   static void radeon_hotplug_work_func(struct work_struct *work)
>   {
>   	struct radeon_device *rdev = container_of(work, struct radeon_device,
> -						  hotplug_work);
> +						  hotplug_work.work);
>   	struct drm_device *dev = rdev->ddev;
>   	struct drm_mode_config *mode_config = &dev->mode_config;
>   	struct drm_connector *connector;
> @@ -302,7 +302,7 @@ int radeon_irq_kms_init(struct radeon_device *rdev)
>   		}
>   	}
>   
> -	INIT_WORK(&rdev->hotplug_work, radeon_hotplug_work_func);
> +	INIT_DELAYED_WORK(&rdev->hotplug_work, radeon_hotplug_work_func);
>   	INIT_WORK(&rdev->dp_work, radeon_dp_work_func);
>   	INIT_WORK(&rdev->audio_work, r600_audio_update_hdmi);
>   
> @@ -310,7 +310,7 @@ int radeon_irq_kms_init(struct radeon_device *rdev)
>   	r = drm_irq_install(rdev->ddev, rdev->ddev->pdev->irq);
>   	if (r) {
>   		rdev->irq.installed = false;
> -		flush_work(&rdev->hotplug_work);
> +		flush_delayed_work(&rdev->hotplug_work);
>   		return r;
>   	}
>   
> @@ -333,7 +333,7 @@ void radeon_irq_kms_fini(struct radeon_device *rdev)
>   		rdev->irq.installed = false;
>   		if (rdev->msi_enabled)
>   			pci_disable_msi(rdev->pdev);
> -		flush_work(&rdev->hotplug_work);
> +		flush_delayed_work(&rdev->hotplug_work);
>   	}
>   }
>   
> diff --git a/drivers/gpu/drm/radeon/radeon_mode.h b/drivers/gpu/drm/radeon/radeon_mode.h
> index 457b026..0aeb3ee 100644
> --- a/drivers/gpu/drm/radeon/radeon_mode.h
> +++ b/drivers/gpu/drm/radeon/radeon_mode.h
> @@ -553,6 +553,7 @@ struct radeon_connector {
>   	void *con_priv;
>   	bool dac_load_detect;
>   	bool detected_by_load; /* if the connection status was determined by load */
> +	bool detected_hpd_without_ddc; /* if an HPD signal was detected on DVI, but ddc probing failed */
>   	uint16_t connector_object_id;
>   	struct radeon_hpd hpd;
>   	struct radeon_router router;
> diff --git a/drivers/gpu/drm/radeon/rs600.c b/drivers/gpu/drm/radeon/rs600.c
> index 97a9048..6244f4e 100644
> --- a/drivers/gpu/drm/radeon/rs600.c
> +++ b/drivers/gpu/drm/radeon/rs600.c
> @@ -813,7 +813,7 @@ int rs600_irq_process(struct radeon_device *rdev)
>   		status = rs600_irq_ack(rdev);
>   	}
>   	if (queue_hotplug)
> -		schedule_work(&rdev->hotplug_work);
> +		schedule_delayed_work(&rdev->hotplug_work, 0);
>   	if (queue_hdmi)
>   		schedule_work(&rdev->audio_work);
>   	if (rdev->msi_enabled) {
> diff --git a/drivers/gpu/drm/radeon/si.c b/drivers/gpu/drm/radeon/si.c
> index 07037e3..fb1a7ec 100644
> --- a/drivers/gpu/drm/radeon/si.c
> +++ b/drivers/gpu/drm/radeon/si.c
> @@ -6848,7 +6848,7 @@ restart_ih:
>   	if (queue_dp)
>   		schedule_work(&rdev->dp_work);
>   	if (queue_hotplug)
> -		schedule_work(&rdev->hotplug_work);
> +		schedule_delayed_work(&rdev->hotplug_work, 0);
>   	if (queue_thermal && rdev->pm.dpm_enabled)
>   		schedule_work(&rdev->pm.dpm.thermal.work);
>   	rdev->ih.rptr = rptr;