Re: [PATCH] Revert "drm/i915: fix infinite loop at gen6_update_ring_freq"

[Ben Widawsky <ben@bwidawsk.net>]

On Thu, Apr 10, 2014 at 09:04:47AM +0200, Daniel Vetter wrote:
> This reverts commit 4b28a1f3ef55a3b0b68dbab1fe6dbaf18e186710.
> 
> This patch duct-tapes over some issue in the current bdw rps patches
> which must wait with enabling rc6/rps until the very first batch has
> been submitted by userspace.
> 
> But those patches aren't merged yet, and for upstream we need to have
> an in-kernel emission of the very first batch. I shouldn't have
> merged this patch so let's revert it again.

I said this on the mailing last before you merged the patch.

> 
> Also Imre noticed that even when rps is set up normally there's a
> small window (due to the 1s delay of the async rps init work) where we
> could runtime suspend already and blow up all over the place. Imre has
> a proper fix to block runtime pm until the rps init work has
> successfully completed.
> 
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Cc: Imre Deak <imre.deak@intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 8531cf6e2774..dc7adadbb945 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3522,8 +3522,7 @@ void gen6_update_ring_freq(struct drm_device *dev)
>  	 * to use for memory access.  We do this by specifying the IA frequency
>  	 * the PCU should use as a reference to determine the ring frequency.
>  	 */
> -	for (gpu_freq = dev_priv->rps.max_freq_softlimit;
> -	     gpu_freq >= dev_priv->rps.min_freq_softlimit && gpu_freq != 0;
> +	for (gpu_freq = dev_priv->rps.max_freq_softlimit; gpu_freq >= dev_priv->rps.min_freq_softlimit;
>  	     gpu_freq--) {
>  		int diff = dev_priv->rps.max_freq_softlimit - gpu_freq;
>  		unsigned int ia_freq = 0, ring_freq = 0;
> -- 
> 1.8.5.2
> 
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-- 
Ben Widawsky, Intel Open Source Technology Center