On Mon, Jan 09, 2017 at 06:06:57PM +0100, Maarten Lankhorst wrote:
> We're protected by the connection_mutex lock against blocking modesets,
> but nonblocking modesets are performed without any locking. This is
> causing WARN in drm_wait_for_vblank and in general it's better to wait
> before modeset completes before trying anything.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 51 +++++++++++++++++++++++++++++++----------
> 1 file changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index fb12896bafee..71882d887393 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4080,24 +4080,38 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
> struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
> struct drm_device *dev = intel_dp_to_dev(intel_dp);
> u8 link_status[DP_LINK_STATUS_SIZE];
> + struct drm_modeset_acquire_ctx ctx;
> + struct intel_connector *intel_connector = intel_dp->attached_connector;
> + int ret;
> + struct drm_crtc *crtc;
>
> - WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
> + drm_modeset_acquire_init(&ctx, 0);
> +
> +retry:
> + ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
> + if (ret)
> + goto out;
>
> if (!intel_dp_get_link_status(intel_dp, link_status)) {
> DRM_ERROR("Failed to get link status\n");
> - return;
> + goto out;
> }
>
> - if (!intel_encoder->base.crtc)
> - return;
> + crtc = intel_connector->base.state->crtc;
> + if (!crtc)
> + goto out;
>
> - if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> - return;
> + ret = drm_modeset_lock(&crtc->mutex, &ctx);
> + if (ret)
> + goto out;
> +
> + if (!crtc->state->active)
> + goto out;
>
> /* FIXME: we need to synchronize this sort of stuff with hardware
> * readout. Currently fast link training doesn't work on boot-up. */
> if (!intel_dp->lane_count)
> - return;
> + goto out;
>
> /* if link training is requested we should perform it always */
> if ((intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) ||
> @@ -4105,8 +4119,26 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
> DRM_DEBUG_KMS("%s: channel EQ not ok, retraining\n",
> intel_encoder->base.name);
>
> + if (drm_atomic_crtc_needs_modeset(crtc->state)) {
> + /* wait for atomic modeset to complete */
> + ret = drm_atomic_helper_wait_for_hw_done(crtc);
> + if (ret < 0)
> + DRM_ERROR("Waiting for hw_done timed out\n");
I wonder if we should just skip the hw frobbing in this case. I guess it
might still restore the link if the commit just somehow got stuck
somewhere non-critical.
> + }
> +
> intel_dp_retrain_link(intel_dp);
> }
> +
> +out:
> + if (ret == -EDEADLK) {
> + drm_modeset_backoff(&ctx);
> + goto retry;
> + }
> +
> + drm_modeset_drop_locks(&ctx);
> + drm_modeset_acquire_fini(&ctx);
> + if (ret)
> + DRM_ERROR("Locking failed with %i\n", ret);
This seems incorrect if we timed out on the wait. Maybe just
clear ret after the hw_done wait?
> }
>
> /*
> @@ -4125,7 +4157,6 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
> static bool
> intel_dp_short_pulse(struct intel_dp *intel_dp)
> {
> - struct drm_device *dev = intel_dp_to_dev(intel_dp);
> u8 sink_irq_vector = 0;
> u8 old_sink_count = intel_dp->sink_count;
> bool ret;
> @@ -4164,9 +4195,7 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
> DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
> }
>
> - drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> intel_dp_check_link_status(intel_dp);
> - drm_modeset_unlock(&dev->mode_config.connection_mutex);
>
> return true;
> }
> @@ -4499,9 +4528,7 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
> * check links status, there has been known issues of
> * link loss triggerring long pulse!!!!
> */
> - drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> intel_dp_check_link_status(intel_dp);
> - drm_modeset_unlock(&dev->mode_config.connection_mutex);
> goto out;
> }
>
> --
> 2.7.4
>
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> dri-devel@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Ville Syrjälä
Intel OTC
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