[Intel-gfx] [PATCH 053/190] drm/i915: Convert i915_semaphores_is_enabled over to early sanitize

[Dave Gordon]

On 11/01/16 09:17, Chris Wilson wrote:
> Rather than recomputing whether semaphores are enabled, we can do that
> computation once during early initialisation as the i915.semaphores
> module parameter is now read-only.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/i915_debugfs.c     |  2 +-
>   drivers/gpu/drm/i915/i915_dma.c         |  2 +-
>   drivers/gpu/drm/i915/i915_drv.c         | 25 -----------------------
>   drivers/gpu/drm/i915/i915_drv.h         |  1 -
>   drivers/gpu/drm/i915/i915_gem.c         | 35 ++++++++++++++++++++++++++++++---
>   drivers/gpu/drm/i915/i915_gem_context.c |  2 +-
>   drivers/gpu/drm/i915/i915_gpu_error.c   |  2 +-
>   drivers/gpu/drm/i915/intel_ringbuffer.c | 20 +++++++++----------
>   8 files changed, 46 insertions(+), 43 deletions(-)

LGTM.

Reviewed-by: Dave Gordon <david.s.gordon at intel.com>

[aside]
The conditions below seem to exclude a lot of systems. It looks like 
semaphores can only be used on GEN 6 (if no IOMMU) and GEN 7. Nothing 
before or after that range, as GEN9+ supports execlist only.

So is it even worth continuing to support semaphores at all? Especially 
as we have customers who say that the scheduler gives more performance 
gain than semaphores ...
[/aside]

.Dave.

> +static bool i915_gem_sanitize_semaphore(struct drm_i915_private *dev_priv,
> +					int param_value)
> +{
> +	if (INTEL_INFO(dev_priv)->gen < 6)
> +		return false;
> +
> +	if (param_value >= 0)
> +		return param_value;
> +
> +	/* TODO: make semaphores and Execlists play nicely together */
> +	if (i915.enable_execlists)
> +		return false;
> +
> +	/* Until we get further testing... */
> +	if (IS_GEN8(dev_priv))
> +		return false;
> +
> +#ifdef CONFIG_INTEL_IOMMU
> +	/* Enable semaphores on SNB when IO remapping is off */
> +	if (INTEL_INFO(dev_priv)->gen == 6 && intel_iommu_gfx_mapped)
> +		return false;
> +#endif
> +
> +	return true;
> +}