nvk: Add an NVK_DEBUG=no_compression flag

docs/drivers/nvk.rst

@@ -76,6 +76,8 @@ specific to NVK:
    ``coherent``
       Forces all memory maps to be coherent with the CPU caches.  This only
       applies to Tegra devices.
+   ``no_compression``
+      Disables image compression.
 
 .. envvar:: NVK_I_WANT_A_BROKEN_VULKAN_DRIVER
 

src/nouveau/vulkan/nvk_debug.h

@@ -42,6 +42,9 @@ enum nvk_debug {
 
    /* Force all memory allocations to go to GART */
    NVK_DEBUG_FORCE_COHERENT = 1ull << 8,
+
+   /* Disable image compression */
+   NVK_DEBUG_NO_COMPRESSION = 1ull << 9,
 };
 
 #endif /* NVK_DEBUG_H */

src/nouveau/vulkan/nvk_image.c

@@ -776,6 +776,9 @@ static bool
 nvk_image_can_compress(const struct nvk_physical_device *pdev,
                        const struct nvk_image *image)
 {
+   if (pdev->debug_flags & NVK_DEBUG_NO_COMPRESSION)
+      return false;
+
    if (!pdev->nvkmd->kmd_info.has_compression)
       return false;
 

src/nouveau/vulkan/nvk_instance.c

@@ -91,6 +91,7 @@ nvk_init_debug_flags(struct nvk_instance *instance)
       { "edb_bview", NVK_DEBUG_FORCE_EDB_BVIEW },
       { "gart", NVK_DEBUG_FORCE_GART },
       { "coherent", NVK_DEBUG_FORCE_COHERENT },
+      { "no_compression", NVK_DEBUG_NO_COMPRESSION },
       { NULL, 0 },
    };