[Intel-gfx] [CI] drm/i915: Disable snooping (userptr, set-cache-level) on gen4

[Daniel Vetter]

On Wed, Sep 06, 2017 at 08:24:24PM +0100, Chris Wilson wrote:
> The original gen4 has an issue where writes (both render and blt) into
> snoopable pages are lost. We've previously worked around this in
> userspace (ddx, igt) by simply not requesting snoopable buffers, but upon
> rediscovering this problem for a third time, make the kernel reject such
> requests with -ENODEV.
> 
> This disables snooping on userspace buffers for i965g and i965gm (original
> gen4) machines.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Cc: stable at vger.kernel.org

(even if greg ignores it ...)
-Daniel
> ---
>  drivers/gpu/drm/i915/i915_pci.c          | 2 ++
>  drivers/gpu/drm/i915/intel_device_info.c | 2 --
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> index 881b5d6708aa..e95baf3c4314 100644
> --- a/drivers/gpu/drm/i915/i915_pci.c
> +++ b/drivers/gpu/drm/i915/i915_pci.c
> @@ -168,6 +168,7 @@ static const struct intel_device_info intel_i965g_info __initconst = {
>  	.platform = INTEL_I965G,
>  	.has_overlay = 1,
>  	.hws_needs_physical = 1,
> +	.has_snoop = false,
>  };
>  
>  static const struct intel_device_info intel_i965gm_info __initconst = {
> @@ -177,6 +178,7 @@ static const struct intel_device_info intel_i965gm_info __initconst = {
>  	.has_overlay = 1,
>  	.supports_tv = 1,
>  	.hws_needs_physical = 1,
> +	.has_snoop = false,
>  };
>  
>  static const struct intel_device_info intel_g45_info __initconst = {
> diff --git a/drivers/gpu/drm/i915/intel_device_info.c b/drivers/gpu/drm/i915/intel_device_info.c
> index b17f7045c8f8..43831b09b47a 100644
> --- a/drivers/gpu/drm/i915/intel_device_info.c
> +++ b/drivers/gpu/drm/i915/intel_device_info.c
> @@ -412,8 +412,6 @@ void intel_device_info_runtime_init(struct drm_i915_private *dev_priv)
>  	else if (INTEL_INFO(dev_priv)->gen >= 9)
>  		gen9_sseu_info_init(dev_priv);
>  
> -	WARN_ON(info->has_snoop != !info->has_llc);
> -
>  	DRM_DEBUG_DRIVER("slice mask: %04x\n", info->sseu.slice_mask);
>  	DRM_DEBUG_DRIVER("slice total: %u\n", hweight8(info->sseu.slice_mask));
>  	DRM_DEBUG_DRIVER("subslice total: %u\n",
> -- 
> 2.14.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch