docs/anv: list environment variables

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14522>

docs/drivers/anv.rst

@@ -1,6 +1,37 @@
 ANV
 ===
 
+Debugging
+---------
+
+Here are a few environment variable debug environment variables
+specific to Anv:
+
+:envvar:`ANV_ENABLE_PIPELINE_CACHE`
+   If defined to ``0`` or ``false``, this will disable pipeline
+   caching, forcing Anv to reparse and recompile any VkShaderModule
+   (SPIRV) it is given.
+:envvar:`ANV_DISABLE_SECONDARY_CMD_BUFFER_CALLS`
+   If defined to ``1`` or ``true``, this will prevent usage of self
+   modifying command buffers to implement ``vkCmdExecuteCommands``. As
+   a result of this, it will also disable ``VK_KHR_performance_query``.
+:envvar:`ANV_ALWAYS_BINDLESS`
+   If defined to ``1`` or ``true``, this forces all descriptor sets to
+   use the internal `Bindless model`_.
+:envvar:`ANV_QUEUE_THREAD_DISABLE`
+   If defined to ``1`` or ``true``, this disables support for timeline
+   semaphores.
+:envvar:`ANV_USERSPACE_RELOCS`
+   If defined to ``1`` or ``true``, this forces Anv to always do
+   kernel relocations in command buffers. This should only have an
+   effect on hardware that doesn't support soft-pinning (Ivybridge,
+   Haswell, Cherryview).
+:envvar:`ANV_PRIMITIVE_REPLICATION_MAX_VIEWS`
+   Specifies up to how many view shaders can be lowered to handle
+   VK_KHR_multiview. Beyond this number, multiview is implemented
+   using instanced rendering. If unspecified, the value default to
+   ``2``.
+
 .. _`Bindless model`:
 
 Binding Model