[Intel-gfx] [PATCH] drm/i915: Only warn for might_sleep() before a slow wait_for_register

[Pandiyan, Dhinakaran]

On Wed, 2018-03-28 at 18:53 +0100, Chris Wilson wrote:
> As intel_wait_for_register_fw() may use, and if successful only use, a
> busy-wait loop, the might_sleep() warning is a little over-zealous.
> Restrict it to a might_sleep_if() a slow timeout is specified (and so
> the caller authorises use of a usleep).
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_uncore.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index f37ecfc69e49..44c4654443ba 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -1996,7 +1996,7 @@ int __intel_wait_for_register(struct drm_i915_private *dev_priv,
>  	u32 reg_value;
>  	int ret;
>  
> -	might_sleep();
> +	might_sleep_if(slow_timeout_ms);

__wait_for() already has a might_sleep(), why is this needed?

>  
>  	spin_lock_irq(&dev_priv->uncore.lock);
>  	intel_uncore_forcewake_get__locked(dev_priv, fw);
> @@ -2008,7 +2008,7 @@ int __intel_wait_for_register(struct drm_i915_private *dev_priv,
>  	intel_uncore_forcewake_put__locked(dev_priv, fw);
>  	spin_unlock_irq(&dev_priv->uncore.lock);
>  
> -	if (ret)
> +	if (ret && slow_timeout_ms)
>  		ret = __wait_for(reg_value = I915_READ_NOTRACE(reg),
>  				 (reg_value & mask) == value,
>  				 slow_timeout_ms * 1000, 10, 1000);