linux-kernel - [PATCH] drm/i915: Synchronize hpd work in i915_hpd_storm_ctl

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Date:   Tue, 20 Nov 2018 19:37:17 -0500
From:   Lyude Paul <lyude@...hat.com>
To:     intel-gfx@...ts.freedesktop.org
Cc:     Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/i915: Synchronize hpd work in i915_hpd_storm_ctl_show()

While trying to add a chamelium test for short HPD IRQs, I ran into
issues where a hotplug storm would be triggered, but the point at which
it would be reported by the kernel would be after igt actually finished
checking i915_hpd_storm_ctl's status. So, fix this by simply
synchronizing our IRQ work, dig_port_work, and hotplug_work before
printing out the HPD storm status in i915_hpd_storm_ctl_show().

Signed-off-by: Lyude Paul <lyude@...hat.com>
Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 69447c68b9af..af4268a6d2d9 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -4592,6 +4592,13 @@ static int i915_hpd_storm_ctl_show(struct seq_file *m, void *data)
 	struct drm_i915_private *dev_priv = m->private;
 	struct i915_hotplug *hotplug = &dev_priv->hotplug;
 
+	/* Synchronize with everything first in case there's been an HPD
+	 * storm, but we haven't finished handling it in the kernel yet
+	 */
+	synchronize_irq(dev_priv->drm.irq);
+	flush_work(&dev_priv->hotplug.dig_port_work);
+	flush_work(&dev_priv->hotplug.hotplug_work);
+
 	seq_printf(m, "Threshold: %d\n", hotplug->hpd_storm_threshold);
 	seq_printf(m, "Detected: %s\n",
 		   yesno(delayed_work_pending(&hotplug->reenable_work)));
-- 
2.19.1