[Intel-gfx] [PATCH v2] drm/i915/lmem: add the fake lmem region

[Chris Wilson]

Quoting Matthew Auld (2019-10-30 17:33:20)
> Intended for upstream testing so that we can still exercise the LMEM
> plumbing and !i915_ggtt_has_aperture paths. Smoke tested on Skull Canyon
> device. This works by allocating an intel_memory_region for a reserved
> portion of system memory, which we treat like LMEM. For the LMEMBAR we
> steal the aperture and 1:1 it map to the stolen region.
> 
> To enable simply set the i915 modparam fake_lmem_start= on the kernel
> cmdline with the start of reserved region(see memmap=). The size of the
> region we can use is determined by the size of the mappable aperture, so
> the size of reserved region should be >= mappable_end. For now we only
> enable for the selftests. Depends on CONFIG_DRM_I915_UNSTABLE being
> enabled.

And trybot with

@@ -37,6 +37,9 @@ config DRM_I915_DEBUG
        select DRM_I915_DEBUG_RUNTIME_PM
        select DRM_I915_DEBUG_MMIO
        select BROKEN # for prototype uAPI
+       select STAGING
+       select DRM_I915_UNSTABLE
+       select DRM_I915_UNSTABLE_FAKE_LMEM
        default n
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