What if you fired the uevent regardless of the previous state? > On Jun 11, 2015, at 2:35 AM, Jani Nikula <jani.nikula@xxxxxxxxx> wrote: > > Currently it's possible this happens when a (non-DP) cable is unplugged: > > - user starts unplugging cable > - hotplug irq fires > - hotplug work function runs > - connector detect function runs > - ddc pin is still connected, edid read succeeds > -> we decide nothing changed, no uevent > - cable completely unplugged > -> our state is inconsistent with reality, no power save > > The user plugs cable back in: > > - most of the same at first > - ddc pin connected, edid read succeeds > -> we decide nothing changed because we thought the cable was plugged > in all along, no uevent > - cable completely plugged > -> our state is somewhat consistent, however monitor might be > different, the link might not recover? > > With our current implementation we rely on the hotplug pin being *both* > the last to be connected on plug *and* last to be disconnected on > unplug. The educated guess is that this is not the case. > > Per the logs in the case of the referenced bug, the hdmi detect code > runs within a few *microseconds* after the hotplug irq, and the EDID has > been successfully read within 25 ms of the irq. If the DDC lines are > still connected when the hotplug irq fires, the user has to be blazingly > fast to complete the unplug before the detect code runs. > > We can afford to wait a little before queuing the work function for a > bit more reliability. Obviously it's still possible for the user to > unplug the cable really slowly, but let's at least give the user a > fighting chance to unplug fast enough. > > I'd love to claim the proposed delay of 400 ms is based on real life > measured data and rigorous analysis, but in truth it is just a gut > feeling based compromise between solving the issue and meeting some > vague real time human interaction deadline for having a picture on > screen. (However I expect any criticism to be more substantiated than > "my gut feeling is better than yours".) > > An alternative would be to check the hotplug state in the irq handler, > but there have been reliability problems with it in the past, and we've > opted not to use it. [citation needed] > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82593 > Tested-by: Hugh Greenberg <hugegreenbug@xxxxxxxxx> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_drv.c | 2 +- > drivers/gpu/drm/i915/i915_drv.h | 2 +- > drivers/gpu/drm/i915/i915_irq.c | 12 ++++++++---- > 3 files changed, 10 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c > index 78ef0bb53c36..002767ddfe06 100644 > --- a/drivers/gpu/drm/i915/i915_drv.c > +++ b/drivers/gpu/drm/i915/i915_drv.c > @@ -552,7 +552,7 @@ void intel_hpd_cancel_work(struct drm_i915_private *dev_priv) > spin_unlock_irq(&dev_priv->irq_lock); > > cancel_work_sync(&dev_priv->hotplug.dig_port_work); > - cancel_work_sync(&dev_priv->hotplug.hotplug_work); > + cancel_delayed_work_sync(&dev_priv->hotplug.hotplug_work); > cancel_delayed_work_sync(&dev_priv->hotplug.reenable_work); > } > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index 611fbd86c1cc..a8a99f658772 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -221,7 +221,7 @@ enum hpd_pin { > for ((__pin) = (HPD_NONE + 1); (__pin) < HPD_NUM_PINS; (__pin)++) > > struct i915_hotplug { > - struct work_struct hotplug_work; > + struct delayed_work hotplug_work; > > struct { > unsigned long last_jiffies; > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > index 56db9e747464..bab67c279c22 100644 > --- a/drivers/gpu/drm/i915/i915_irq.c > +++ b/drivers/gpu/drm/i915/i915_irq.c > @@ -828,6 +828,8 @@ static bool intel_hpd_irq_event(struct drm_device *dev, > return true; > } > > +#define HOTPLUG_DELAY_MS 400 > + > static void i915_digport_work_func(struct work_struct *work) > { > struct drm_i915_private *dev_priv = > @@ -872,7 +874,8 @@ static void i915_digport_work_func(struct work_struct *work) > spin_lock_irq(&dev_priv->irq_lock); > dev_priv->hotplug.event_bits |= old_bits; > spin_unlock_irq(&dev_priv->irq_lock); > - schedule_work(&dev_priv->hotplug.hotplug_work); > + mod_delayed_work(system_wq, &dev_priv->hotplug.hotplug_work, > + msecs_to_jiffies(HOTPLUG_DELAY_MS)); > } > } > > @@ -884,7 +887,7 @@ static void i915_digport_work_func(struct work_struct *work) > static void i915_hotplug_work_func(struct work_struct *work) > { > struct drm_i915_private *dev_priv = > - container_of(work, struct drm_i915_private, hotplug.hotplug_work); > + container_of(work, struct drm_i915_private, hotplug.hotplug_work.work); > struct drm_device *dev = dev_priv->dev; > struct drm_mode_config *mode_config = &dev->mode_config; > struct intel_connector *intel_connector; > @@ -1601,7 +1604,8 @@ static void intel_hpd_irq_handler(struct drm_device *dev, > if (queue_dig) > queue_work(dev_priv->hotplug.dp_wq, &dev_priv->hotplug.dig_port_work); > if (queue_hp) > - schedule_work(&dev_priv->hotplug.hotplug_work); > + mod_delayed_work(system_wq, &dev_priv->hotplug.hotplug_work, > + msecs_to_jiffies(HOTPLUG_DELAY_MS)); > } > > static void gmbus_irq_handler(struct drm_device *dev) > @@ -4397,7 +4401,7 @@ void intel_irq_init(struct drm_i915_private *dev_priv) > { > struct drm_device *dev = dev_priv->dev; > > - INIT_WORK(&dev_priv->hotplug.hotplug_work, i915_hotplug_work_func); > + INIT_DELAYED_WORK(&dev_priv->hotplug.hotplug_work, i915_hotplug_work_func); > INIT_WORK(&dev_priv->hotplug.dig_port_work, i915_digport_work_func); > INIT_WORK(&dev_priv->rps.work, gen6_pm_rps_work); > INIT_WORK(&dev_priv->l3_parity.error_work, ivybridge_parity_work); > -- > 2.1.4 > _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
