Re: [PATCH 2/2] drm/i915: Fix GT wake FIFO free entries for VLV

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thu, 14 Nov 2013 02:00:00 +0200
ville.syrjala@linux.intel.com wrote:

> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> On VLV the GTFIFOCTL register has other bits besides the number of free
> entries in the GT wake FIFO. Apply a mask when we read th register to
> make sure we don't misinterpret the number of free FIFO entries.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h     | 3 ++-
>  drivers/gpu/drm/i915/intel_uncore.c | 6 +++---
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index e8f47de..e243105 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -4860,7 +4860,8 @@
>  #define    GT_FIFO_IAWRERR			(1<<1)
>  #define    GT_FIFO_IARDERR			(1<<0)
>  
> -#define  GT_FIFO_FREE_ENTRIES			0x120008
> +#define  GTFIFOCTL				0x120008
> +#define    GT_FIFO_FREE_ENTRIES_MASK		0x7f
>  #define    GT_FIFO_NUM_RESERVED_ENTRIES		20
>  
>  #define  HSW_IDICR				0x9008
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index a9849ab..71902c4 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -148,10 +148,10 @@ static int __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv)
>  
>  	if (dev_priv->uncore.fifo_count < GT_FIFO_NUM_RESERVED_ENTRIES) {
>  		int loop = 500;
> -		u32 fifo = __raw_i915_read32(dev_priv, GT_FIFO_FREE_ENTRIES);
> +		u32 fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
>  		while (fifo <= GT_FIFO_NUM_RESERVED_ENTRIES && loop--) {
>  			udelay(10);
> -			fifo = __raw_i915_read32(dev_priv, GT_FIFO_FREE_ENTRIES);
> +			fifo = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
>  		}
>  		if (WARN_ON(loop < 0 && fifo <= GT_FIFO_NUM_RESERVED_ENTRIES))
>  			++ret;
> @@ -806,7 +806,7 @@ static int gen6_do_reset(struct drm_device *dev)
>  		dev_priv->uncore.funcs.force_wake_put(dev_priv);
>  
>  	/* Restore fifo count */
> -	dev_priv->uncore.fifo_count = __raw_i915_read32(dev_priv, GT_FIFO_FREE_ENTRIES);
> +	dev_priv->uncore.fifo_count = __raw_i915_read32(dev_priv, GTFIFOCTL) & GT_FIFO_FREE_ENTRIES_MASK;
>  
>  	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
>  	return ret;

I don't see this reg on HSW, but it looks like our HSW code uses this
routine?

Assuming the spec is just broken today... at least I see it for other
gens.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

-- 
Jesse Barnes, Intel Open Source Technology Center
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