Re: [PATCH] drm/i915: Synchronize hpd work in i915_hpd_storm_ctl_show()

[Daniel Vetter]

On Tue, Nov 20, 2018 at 07:37:17PM -0500, Lyude Paul wrote:
> 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@xxxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>

Makes sense.

Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

> ---
>  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
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch