From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [PATCH 2/8] drm/i915: fixup up debugfs rps state
	handling
Date: Thu, 09 Aug 2012 10:32:21 +0100
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Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
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On Wed,  8 Aug 2012 23:35:34 +0200, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> - Take the dev->struct_mutex around access the corresponding state
>   (and adjusting the rps hw state).
> - Add an assert to gen6_set_rps to ensure we don't forget about this
>   in the future.
> - Don't set up the min/max_freq files if it doesn't apply to the hw.
>   And do the same for the gen6+ cache sharing file while at it.
> 
> v2: Move the gen6+ checks into the read/write callbacks. Thanks to the
> awesome drm midlayer we can't check that when registering the debugfs
> files, because the driver is not yet fully set up, specifically the
> ->load callback hasn't run yet.
> 
> Oh how I despise this disaster ...
> 
> v3: Also add a WARN_ON(mutex_is_locked) in set_rps to check the
> locking.
> 
> Reviewed-by: Ben Widawsky <ben@bwidawsk.net> (for v2)
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c |   27 +++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_pm.c     |    2 ++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 1312b79..2499610 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -1710,8 +1710,13 @@ i915_max_freq_read(struct file *filp,
>  	char buf[80];
>  	int len;
>  
> +	if (!(IS_GEN6(dev) || IS_GEN7(dev)))
> +		return -ENODEV;
> +
> +	mutex_lock(&dev->struct_mutex);

In debugfs, I advise that we use mutex_lock_interruptible().
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre