Mesa (master): anv: advertise 8 subtexel/mipmap precision bits
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Tue Apr 9 15:35:30 UTC 2019
Module: Mesa
Branch: master
Commit: ec7a33af58dbf421c58dfcc65c680e9c2f1ce09a
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=ec7a33af58dbf421c58dfcc65c680e9c2f1ce09a
Author: Juan A. Suarez Romero <jasuarez at igalia.com>
Date: Tue Apr 9 15:28:42 2019 +0000
anv: advertise 8 subtexel/mipmap precision bits
So far ANV was advertising 4 bits for both subTexelPrecisionBits and
mipmapPrecisionBits. But these values were not actually verified.
But it seems the right value is actually 8 bits for both cases.
Unfortunately Intel PRM does not clarify how many bits the hardware use.
For the mipmap case, there is the following reference in PRM Volume 6
(3D Media GPGPU), specifically in LOD Computation Pseudocode:
```
Bias: S4.8
MinLod: U4.8
MaxLod: U4.8
Base: U4.1
MIPCnt: U4
SurfMinLod: U4.8
ResMinLod: U4.8
``
We have other clues, though:
- On one side, dEQP-VK.texture.explicit_lod.* tests fail when using 4
bits, but work when using 8 bits. These tests try to mimic the expected
behaviour as much real as possible, and they use the reported
subTexelPrecisionBits and mipmapPrecisionBits reported to get this.
- On the other side, the equivalent driver for Windows is reporting 8
bits for both elements. Not sure if they got to verify it from the PRM
or from a diffent source.
CC: Jason Ekstrand <jason at jlekstrand.net>
CC: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
---
src/intel/vulkan/anv_device.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/intel/vulkan/anv_device.c b/src/intel/vulkan/anv_device.c
index 9d4f93c910f..88b34c49c1c 100644
--- a/src/intel/vulkan/anv_device.c
+++ b/src/intel/vulkan/anv_device.c
@@ -1147,8 +1147,8 @@ void anv_GetPhysicalDeviceProperties(
16 * devinfo->max_cs_threads,
},
.subPixelPrecisionBits = 8,
- .subTexelPrecisionBits = 4 /* FIXME */,
- .mipmapPrecisionBits = 4 /* FIXME */,
+ .subTexelPrecisionBits = 8,
+ .mipmapPrecisionBits = 8,
.maxDrawIndexedIndexValue = UINT32_MAX,
.maxDrawIndirectCount = UINT32_MAX,
.maxSamplerLodBias = 16,
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