Re: [Intel-gfx] [PATCH] drm/i915: Disable FBC on Haswell

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 06 Jun 2014, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> It causes black screen on bootup and is approximately 100x slower than
> running with FBC disabled, so the GPU runs at a high frequency for much
> longer - completely contrary to the power saving claims. It also still
> has mutex deadlocks in multi-head scenarios, which can lead to a
> system/X lockup. These bugs were known before FBC was enabled by default
> on Haswell and still have not been fixed.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79716
> Reported-and-tested-by: Jon Kristensen <info@jonkri.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: stable@vger.kernel.org
> ---
>  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 e403010540a5..0b8a6010427e 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -511,8 +511,7 @@ void intel_update_fbc(struct drm_device *dev)
>  	obj = intel_fb->obj;
>  	adjusted_mode = &intel_crtc->config.adjusted_mode;
>  
> -	if (i915.enable_fbc < 0 &&
> -	    INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev)) {
> +	if (i915.enable_fbc < 0) {

Not only does this disable FBC by default on Haswell but also on all
current and future platforms, including Broadwell. Shouldn't you leave
the INTEL_INFO(dev)->gen <= 7 part intact?

BR,
Jani.


>  		if (set_no_fbc_reason(dev_priv, FBC_CHIP_DEFAULT))
>  			DRM_DEBUG_KMS("disabled per chip default\n");
>  		goto out_disable;
> -- 
> 2.0.0
>
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-- 
Jani Nikula, Intel Open Source Technology Center