Re: [PATCH v2 2/2] drm/i915: Wait for pending modesets to complete before trying link training, v2.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jun 14, 2017 at 11:08:42AM +0200, Maarten Lankhorst wrote:
> The nonblocking modeset tests were failing on systems with a DP output,
> because lijnk training could occur during the modeset.
> 
> With normal modesets we're protected by the connection_mutex lock,
> but nonblocking modesets drop locks before completing. To get around
> that, check if the most recent crtc_state has a modeset, and if this
> is the case, wait for all outstanding atomic updates on that crtc
> to complete.
> 
> This fixes the following spew when running nonblocking tests:
> [ 1061.653778] ------------[ cut here ]------------
> [ 1061.653781] WARNING: CPU: 1 PID: 8165 at
> drivers/gpu/drm/drm_irq.c:1217 drm_wait_one_vblank+0x165/0x1a0
> [ 1061.653782] vblank not available on crtc 0, ret=-22
> [ 1061.653783] Modules linked in: vgem snd_hda_intel i915
> snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic
> x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul
> crc32_pclmul ghash_clmulni_intel snd_hda_codec snd_hwdep snd_hda_core
> snd_pcm mei_me mei e1000e ptp pps_core i2c_hid [last unloaded: vgem]
> [ 1061.653796] CPU: 1 PID: 8165 Comm: kworker/1:3 Tainted: G     U  W
> 4.10.0-rc1-CI-Custom_114+ #1
> [ 1061.653797] Hardware name: GIGABYTE GB-BKi5A-7200/MFLP5AP-00, BIOS F1
> 07/27/2016
> [ 1061.653812] Workqueue: events i915_hpd_poll_init_work [i915]
> [ 1061.653813] Call Trace:
> [ 1061.653816]  dump_stack+0x67/0x92
> [ 1061.653818]  __warn+0xc6/0xe0
> [ 1061.653819]  warn_slowpath_fmt+0x4a/0x50
> [ 1061.653820]  ? drm_vblank_get+0x74/0xc0
> [ 1061.653821]  drm_wait_one_vblank+0x165/0x1a0
> [ 1061.653823]  ? drm_dp_dpcd_write+0x16/0x20
> [ 1061.653837]  ? intel_dp_set_link_train+0x44/0xe0 [i915]
> [ 1061.653851]  intel_dp_check_link_status+0x113/0x1a0 [i915]
> [ 1061.653864]  intel_dp_detect+0x5a1/0xa40 [i915]
> [ 1061.653866]  drm_helper_hpd_irq_event+0x8d/0x110
> [ 1061.653880]  i915_hpd_poll_init_work+0xab/0xd0 [i915]
> [ 1061.653882]  process_one_work+0x1f4/0x6d0
> [ 1061.653883]  ? process_one_work+0x16e/0x6d0
> [ 1061.653885]  worker_thread+0x49/0x4a0
> [ 1061.653886]  kthread+0x107/0x140
> [ 1061.653888]  ? process_one_work+0x6d0/0x6d0
> [ 1061.653889]  ? kthread_create_on_node+0x40/0x40
> [ 1061.653891]  ret_from_fork+0x27/0x40
> [ 1061.653892] ---[ end trace f6037618668d4cbc ]---
> [ 1061.656353] [drm:intel_dp_set_idle_link_train [i915]] *ERROR* Timed out waiting for DP idle patterns
> 
> Changes since v1:
> - intel_dp_detect() now holds connection_mutex and has an acquire_ctx,
>   rewrite patch to take advantage of it.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99272
> Testcase: kms_atomic_transitions.1x-modeset-transitions-nonblocking
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 72 ++++++++++++++++++++++++++++++++++-------
>  1 file changed, 60 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 64fa774c855b..c7a66883e453 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4243,21 +4243,32 @@ static void
>  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 intel_connector *intel_connector = intel_dp->attached_connector;
> +	struct drm_crtc *crtc;
>  
> -	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
> -
> -	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> -		DRM_ERROR("Failed to get link status\n");
> +	crtc = intel_connector->base.state->crtc;
> +	if (!crtc)
>  		return;
> -	}
>  
> -	if (!intel_encoder->base.crtc)
> +	WARN_ON(!drm_modeset_is_locked(&crtc->mutex));
> +
> +	if (!crtc->state->active)
>  		return;
>  
> -	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
> +	if (drm_atomic_crtc_needs_modeset(crtc->state)) {
> +		int ret;
> +
> +		/* 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");
> +	}
> +
> +	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> +		DRM_ERROR("Failed to get link status\n");
>  		return;
> +	}
>  
>  	/*
>  	 * Validate the cached values of intel_dp->link_rate and
> @@ -4291,7 +4302,6 @@ 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);
>  	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
>  	u8 sink_irq_vector = 0;
>  	u8 old_sink_count = intel_dp->sink_count;
> @@ -4331,9 +4341,8 @@ 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);
> +
>  	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
>  		DRM_DEBUG_KMS("Link Training Compliance Test requested\n");
>  		/* Send a Hotplug Uevent to userspace to start modeset */
> @@ -4735,8 +4744,19 @@ intel_dp_detect(struct drm_connector *connector,
>  		      connector->base.id, connector->name);
>  
>  	/* If full detect is not performed yet, do a full detect */
> -	if (!intel_dp->detect_done)
> +	if (!intel_dp->detect_done) {
> +		struct drm_crtc *crtc;
> +		int ret;
> +
> +		crtc = connector->state->crtc;
> +		if (crtc) {
> +			ret = drm_modeset_lock(&crtc->mutex, ctx);
> +			if (ret)
> +				return ret;
> +		}
> +
>  		status = intel_dp_long_pulse(intel_dp->attached_connector);
> +	}
>  
>  	intel_dp->detect_done = false;
>  
> @@ -5028,10 +5048,38 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
>  	}
>  
>  	if (!intel_dp->is_mst) {
> +		struct drm_modeset_acquire_ctx ctx;
> +		struct drm_connector *connector = &intel_dp->attached_connector->base;
> +		struct drm_crtc *crtc;
> +		int iret;
> +
> +		drm_modeset_acquire_init(&ctx, 0);
> +retry:
> +		iret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
> +		if (iret)
> +			goto err;
> +
> +		crtc = connector->state->crtc;
> +		if (crtc) {
> +			iret = drm_modeset_lock(&crtc->mutex, &ctx);

Please no modeset locks in the dig_work. Hmm. Looks like we already have
it there though :( I thought we had moved the link retraining fully into
the hoplug_work, but I guess not. Can you try to do that instead?

> +			if (iret)
> +				goto err;
> +		}
> +
>  		if (!intel_dp_short_pulse(intel_dp)) {
>  			intel_dp->detect_done = false;
>  			goto put_power;
>  		}
> +
> +err:
> +		if (iret == -EDEADLK) {
> +			drm_modeset_backoff(&ctx);
> +			goto retry;
> +		}
> +
> +		drm_modeset_drop_locks(&ctx);
> +		drm_modeset_acquire_fini(&ctx);
> +		WARN(iret, "Acquiring modeset locks failed with %i\n", iret);
>  	}
>  
>  	ret = IRQ_HANDLED;
> -- 
> 2.11.0
> 
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-- 
Ville Syrjälä
Intel OTC
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