[PATCH 4/8] drm/i915/dg1: Reserve first 1MB of local memory

[Chris Wilson]

Quoting Matthew Auld (2021-01-25 18:14:42)
> From: Imre Deak <imre.deak at intel.com>
> 
> On DG1 A0/B0 steppings the first 1MB of local memory must be reserved.
> One reason for this is that the 0xA0000-0xB0000 range is not accessible
> by the display, probably since this region is redirected to another
> memory location for legacy VGA compatibility.
> 
> BSpec: 50586
> Testcase: igt/kms_big_fb/linear-64bpp-rotate-0
> 
> v2:
> - Reserve the memory on B0 as well.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_region_lmem.c | 52 +++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> index 3a990a9506f3..fb1041b82849 100644
> --- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> +++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> @@ -137,6 +137,48 @@ intel_setup_fake_lmem(struct drm_i915_private *i915)
>         return mem;
>  }
>  
> +static void get_legacy_lowmem_region(struct intel_uncore *uncore,
> +                                    u64 *start, u32 *size)
> +{
> +       *start = 0;
> +       *size = 0;
> +
> +       if (!IS_DG1_REVID(uncore->i915, DG1_REVID_A0, DG1_REVID_B0))
> +               return;
> +
> +       *size = SZ_1M;
> +
> +       DRM_DEBUG_DRIVER("LMEM: reserved legacy low-memory [0x%llx-0x%llx]\n",
> +                        *start, *start + *size);

Update all DRM_DEBUG_DRIVER()
-Chris