[Intel-gfx] [PATCH] drm/i915/bdw: Don't use forcewake needlessly

[Ben Widawsky]

On Tue, Dec 10, 2013 at 03:24:52PM +0200, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> Not all registers need forcewake even if they're not shadowed.
> Add the missing NEEDS_FORCE_WAKE() check to gen8_writeX() to
> avoid needless forcewake usage when writing eg. display
> registers.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
> I didn't test this at all, so be warned.
> 
>  drivers/gpu/drm/i915/intel_uncore.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index e63658e..78fe8d6 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -616,7 +616,8 @@ static bool is_gen8_shadowed(struct drm_i915_private *dev_priv, u32 reg)
>  #define __gen8_write(x) \
>  static void \
>  gen8_write##x(struct drm_i915_private *dev_priv, off_t reg, u##x val, bool trace) { \
> -	bool __needs_put = !is_gen8_shadowed(dev_priv, reg); \
> +	bool __needs_put = NEEDS_FORCE_WAKE(dev_priv, reg) && \
> +		!is_gen8_shadowed(dev_priv, reg); \
>  	REG_WRITE_HEADER; \
>  	if (__needs_put) { \
>  		dev_priv->uncore.funcs.force_wake_get(dev_priv, \

I would prefer if this was simply checking the display offset, as
opposed to NEEDS_FORCE_WAKE - since if someone adds to the macro we run
the risk of a potentially hard to track down bug.

In any case, the patch is functionally correct, and I'd prefer the
change, but up to you:
Reviewed-by: Ben Widawsky <ben at bwidawsk.net>

> -- 
> 1.8.3.2
> 
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-- 
Ben Widawsky, Intel Open Source Technology Center