[Intel-gfx] [PATCH] drm/i915: disable set/get_tiling ioctl on gen12+

[Chris Wilson]

Quoting Daniel Vetter (2019-08-20 18:06:31)
> The cpu (de)tiler hw is gone, this stopped being useful. Plus it never
> supported any of the fancy new tiling formats, which means userspace
> also stopped using the magic side-channel this provides.
> 
> This would totally break a lot of the igts, but they're already broken
> for the same reasons as userspace on gen12 would be.
> 
> Cc: Kenneth Graunke <kenneth at whitecape.org>
> Cc: Jason Ekstrand <jason at jlekstrand.net>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Lucas De Marchi <lucas.demarchi at intel.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_tiling.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
> index ca0c2f451742..2ee96f27a294 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
> @@ -313,10 +313,15 @@ int
>  i915_gem_set_tiling_ioctl(struct drm_device *dev, void *data,
>                           struct drm_file *file)
>  {
> +       struct drm_i915_private *dev_priv = to_i915(dev);
>         struct drm_i915_gem_set_tiling *args = data;
>         struct drm_i915_gem_object *obj;
>         int err;
>  
> +       /* there is no cpu (de)tiling in the hw anymore on gen12+ */
> +       if (INTEL_GEN(dev_priv) >= 12)

This should be if (!NUM_FENCES(dev_priv)) if anything. You wouldn't even
need the comment talking about random features, and instead focus on why
not supporting the back channel is worth the maintenance cost of
divergence.

> +               return -EOPNOTSUPP;
> +
>         obj = i915_gem_object_lookup(file, args->handle);
>         if (!obj)
>                 return -ENOENT;
> @@ -402,6 +407,9 @@ i915_gem_get_tiling_ioctl(struct drm_device *dev, void *data,
>         struct drm_i915_gem_object *obj;
>         int err = -ENOENT;
>  
> +       if (INTEL_GEN(dev_priv) >= 12)
> +               return -EOPNOTSUPP;

Not required.
-Chris