[Intel-gfx] [PATCH v2] drm/i915: Avoid HPD poll detect triggering a new detect cycle

[Ville Syrjälä]

On Mon, Oct 28, 2019 at 08:15:17PM +0200, Imre Deak wrote:
> For the HPD interrupt functionality the HW depends on power wells in the
> display core domain to be on. Accordingly when enabling these power
> wells the HPD polling logic will force an HPD detection cycle to account
> for hotplug events that may have happened when such a power well was
> off.
> 
> Thus a detect cycle started by polling could start a new detect cycle if
> a power well in the display core domain gets enabled during detect and
> stays enabled after detect completes. That in turn can lead to a
> detection cycle runaway.
> 
> To prevent re-triggering a poll-detect cycle make sure we drop all power
> references we acquired during detect synchronously by the end of detect.
> This will let the poll-detect logic continue with polling (matching the
> off state of the corresponding power wells) instead of scheduling a new
> detection cycle.
> 
> Fixes: 6cfe7ec02e85 ("drm/i915: Remove the unneeded AUX power ref from intel_dp_detect()")
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112125
> Reported-and-tested-by: Val Kulkov <val.kulkov at gmail.com>
> Reported-and-tested-by: wangqr <wqr.prg at gmail.com>
> Cc: Val Kulkov <val.kulkov at gmail.com>
> Cc: wangqr <wqr.prg at gmail.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Imre Deak <imre.deak at intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_crt.c  | 7 +++++++
>  drivers/gpu/drm/i915/display/intel_dp.c   | 6 ++++++
>  drivers/gpu/drm/i915/display/intel_hdmi.c | 6 ++++++
>  3 files changed, 19 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_crt.c b/drivers/gpu/drm/i915/display/intel_crt.c
> index ff6126ea793c..834bf1d43bb8 100644
> --- a/drivers/gpu/drm/i915/display/intel_crt.c
> +++ b/drivers/gpu/drm/i915/display/intel_crt.c
> @@ -864,6 +864,13 @@ intel_crt_detect(struct drm_connector *connector,
>  
>  out:
>  	intel_display_power_put(dev_priv, intel_encoder->power_domain, wakeref);
> +
> +	/*
> +	 * Make sure the refs for power wells enabled during detect are
> +	 * dropped to avoid a new detect cycle triggered by HPD polling.
> +	 */
> +	intel_display_power_flush_work(dev_priv);
> +
>  	return status;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index 86989ec25bc6..486fe203f56c 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -5688,6 +5688,12 @@ intel_dp_detect(struct drm_connector *connector,
>  	if (status != connector_status_connected && !intel_dp->is_mst)
>  		intel_dp_unset_edid(intel_dp);
>  
> +	/*
> +	 * Make sure the refs for power wells enabled during detect are
> +	 * dropped to avoid a new detect cycle triggered by HPD polling.
> +	 */
> +	intel_display_power_flush_work(dev_priv);
> +
>  	return status;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index b54ccbb5aad5..ff71a4da3d00 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -2626,6 +2626,12 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
>  	if (status != connector_status_connected)
>  		cec_notifier_phys_addr_invalidate(intel_hdmi->cec_notifier);
>  
> +	/*
> +	 * Make sure the refs for power wells enabled during detect are
> +	 * dropped to avoid a new detect cycle triggered by HPD polling.
> +	 */
> +	intel_display_power_flush_work(dev_priv);
> +
>  	return status;
>  }
>  
> -- 
> 2.17.1

-- 
Ville Syrjälä
Intel