On Mon, Feb 25, 2013 at 12:06:53PM -0500, Egbert Eich wrote:
> Add a hotplug IRQ storm detection (triggered when a hotplug interrupt
> fires more than 5 times / sec).
> Mask out this specific interrupt and revert to polling on the associated
> output.
Hmm, not convinced that just marking it as HPD_MARK_DISABLED does that.
It certainly prevents the irq from sending the uevent, but we have not
yet disabled the irq or enabled drm_kms_helper.poll for this connector.
Though userspace polling is unaffected.
> Rationale:
> Despite of the many attempts to fix the problem with noisy hotplug
> interrupt lines we are still seeing systems which have issues:
> Once cause of noise seems to be bad routing of the hotplug line
> on the board: cross talk from other signals seems to cause erronous
> hotplug interrupts. This has been documented as an erratum for the
> the i945GM chipset and thus hotplug support was disabled for this
> chipset model but others seem to have this problem, too.
>
> We have seen this issue on a G35 motherboard for example:
> Even different motherboards of the same model seem to behave
> differently: while some only see only around 10-100 interrupts/s
> others seem to see 5k or more.
> We've also observed a dependency on the selected video mode.
>
> Also on certain laptops interrupt noise seems to occur duing
> battery charging when the battery is at a certain charge levels.
>
> Thus we add a simple algorithm here that detects an 'interrupt storm'
> condition.
Looks sane.
>
> Signed-off-by: Egbert Eich <eich at suse.de>
> ---
> drivers/gpu/drm/i915/i915_drv.h | 9 +++++
> drivers/gpu/drm/i915/i915_irq.c | 63 +++++++++++++++++++++++++++++++-------
> 2 files changed, 60 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d8604a6..6ca742d 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1059,6 +1059,15 @@ typedef struct drm_i915_private {
> /* Old dri1 support infrastructure, beware the dragons ya fools entering
> * here! */
> struct i915_dri1_state dri1;
> + struct {
> + unsigned long hpd_last_jiffies;
> + int hpd_cnt;
> + enum {
> + HPD_ENABLED = 0,
> + HPD_DISABLED = 1,
> + HPD_MARK_DISABLED = 2
> + } hpd_mark;
> + } hpd_stats[HPD_NUM_PINS];
Please don't put it below dri1 -- as it may then be confused with our
legacy burden.
> } drm_i915_private_t;
>
> /* Iterate over initialised rings */
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index c6ae7ae..08a0934 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -587,6 +587,34 @@ static void gen6_queue_rps_work(struct drm_i915_private *dev_priv,
> queue_work(dev_priv->wq, &dev_priv->rps.work);
> }
>
> +static inline void hotplug_irq_storm_detect(struct drm_device *dev,
> + u32 hotplug_trigger,
> + const u32 *hpd)
> +{
> + drm_i915_private_t *dev_priv = dev->dev_private;
> + unsigned long irqflags;
> + int i;
> +
> + spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
> +
> + for (i = 1; i < HPD_NUM_PINS; i++) {
> + if ((hpd[i] & hotplug_trigger) &&
> + dev_priv->hpd_stats[i].hpd_mark == HPD_ENABLED) {
> + if (jiffies > (dev_priv->hpd_stats[i].hpd_last_jiffies + msecs_to_jiffies(1000)) ||
> + jiffies < dev_priv->hpd_stats[i].hpd_last_jiffies) {
if (time_is_after(dev_priv->hpd_stats[i].hpd_last_jiffies + msecs_to_jiffies(1000)))
Though it would be simpler if we just stored the adjusted
hpd_last_jiffies.
> + dev_priv->hpd_stats[i].hpd_last_jiffies = jiffies;
> + dev_priv->hpd_stats[i].hpd_cnt = 0;
> + } else if (dev_priv->hpd_stats[i].hpd_cnt > 5) {
> + dev_priv->hpd_stats[i].hpd_mark = HPD_MARK_DISABLED;
> + DRM_DEBUG_KMS("HPD interrupt storm detected on PIN %d\n", i);
> + } else
> + dev_priv->hpd_stats[i].hpd_cnt++;
> + }
> + }
> +
> + spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
> +}
--
Chris Wilson, Intel Open Source Technology Centre
