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.kul...@gmail.com>
> Reported-and-tested-by: wangqr <wqr....@gmail.com>
> Cc: Val Kulkov <val.kul...@gmail.com>
> Cc: wangqr <wqr....@gmail.com>
> Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> Signed-off-by: Imre Deak <imre.d...@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrj...@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
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