[mutter] backend/native: Only disable KMS modifiers for i915

[Marge Bot <marge-bot src gnome org>]

commit da3baba9806226f4fb9c080d7e986728457733ba
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Mar 19 12:08:21 2021 +0100

    backend/native: Only disable KMS modifiers for i915
    
    The intel DRM driver is known for not being able to handle multi head
    setups when KMS modifiers are enabled, due to the implicitly selected
    modifiers, while being more suitable for single head setups, cause
    bandwidth issues when a certain number of monitor times resolution and
    refresh rate is configured.
    
    We don't yet support automatically finding a combination of modifiers
    that work, and have because of this disabled KMS modifiers unless the
    driver actually needs it.
    
    Lets flip this configuration the other way around, changing the current
    udev rule to decide wen to *disable* KMS modifier support, as it so that
    only the Intel driver has this problem, while on the other hand, there
    several drivers that requires modifiers to function at all.
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1792>

 data/61-mutter.rules                       |  2 +-
 src/backends/native/meta-backend-native.c  |  4 ++--
 src/backends/native/meta-gpu-kms.c         |  4 ++--
 src/backends/native/meta-gpu-kms.h         |  2 +-
 src/backends/native/meta-kms-types.h       |  2 +-
 src/backends/native/meta-renderer-native.c | 18 ++++++++++++++++--
 src/backends/native/meta-udev.c            |  4 ++--
 src/backends/native/meta-udev.h            |  2 +-
 8 files changed, 26 insertions(+), 12 deletions(-)
---
diff --git a/data/61-mutter.rules b/data/61-mutter.rules
index 59cc00007c..99a9cf5134 100644
--- a/data/61-mutter.rules
+++ b/data/61-mutter.rules
@@ -1 +1 @@
-DRIVER=="tegra-host1x", SUBSYSTEM=="platform", TAG+="mutter-device-requires-kms-modifiers"
+DRIVERS=="i915", SUBSYSTEM=="drm", TAG+="mutter-device-disable-kms-modifiers"
diff --git a/src/backends/native/meta-backend-native.c b/src/backends/native/meta-backend-native.c
index dbbedceaeb..f907acd966 100644
--- a/src/backends/native/meta-backend-native.c
+++ b/src/backends/native/meta-backend-native.c
@@ -423,8 +423,8 @@ create_gpu_from_udev_device (MetaBackendNative  *native,
   if (meta_is_udev_device_boot_vga (device))
     flags |= META_KMS_DEVICE_FLAG_BOOT_VGA;
 
-  if (meta_is_udev_device_requires_modifiers (device))
-    flags |= META_KMS_DEVICE_FLAG_REQUIRES_MODIFIERS;
+  if (meta_is_udev_device_disable_modifiers (device))
+    flags |= META_KMS_DEVICE_FLAG_DISABLE_MODIFIERS;
 
   if (meta_is_udev_device_preferred_primary (device))
     flags |= META_KMS_DEVICE_FLAG_PREFERRED_PRIMARY;
diff --git a/src/backends/native/meta-gpu-kms.c b/src/backends/native/meta-gpu-kms.c
index e964b10943..e81c90a022 100644
--- a/src/backends/native/meta-gpu-kms.c
+++ b/src/backends/native/meta-gpu-kms.c
@@ -149,12 +149,12 @@ meta_gpu_kms_is_platform_device (MetaGpuKms *gpu_kms)
 }
 
 gboolean
-meta_gpu_kms_requires_modifiers (MetaGpuKms *gpu_kms)
+meta_gpu_kms_disable_modifiers (MetaGpuKms *gpu_kms)
 {
   MetaKmsDeviceFlag flags;
 
   flags = meta_kms_device_get_flags (gpu_kms->kms_device);
-  return !!(flags & META_KMS_DEVICE_FLAG_REQUIRES_MODIFIERS);
+  return !!(flags & META_KMS_DEVICE_FLAG_DISABLE_MODIFIERS);
 }
 
 static int
diff --git a/src/backends/native/meta-gpu-kms.h b/src/backends/native/meta-gpu-kms.h
index 80957f5a09..f13a141f49 100644
--- a/src/backends/native/meta-gpu-kms.h
+++ b/src/backends/native/meta-gpu-kms.h
@@ -47,7 +47,7 @@ gboolean meta_gpu_kms_is_crtc_active (MetaGpuKms *gpu_kms,
 
 gboolean meta_gpu_kms_is_boot_vga (MetaGpuKms *gpu_kms);
 gboolean meta_gpu_kms_is_platform_device (MetaGpuKms *gpu_kms);
-gboolean meta_gpu_kms_requires_modifiers (MetaGpuKms *gpu_kms);
+gboolean meta_gpu_kms_disable_modifiers (MetaGpuKms *gpu_kms);
 
 MetaKmsDevice * meta_gpu_kms_get_kms_device (MetaGpuKms *gpu_kms);
 
diff --git a/src/backends/native/meta-kms-types.h b/src/backends/native/meta-kms-types.h
index 01db55a402..739aca7801 100644
--- a/src/backends/native/meta-kms-types.h
+++ b/src/backends/native/meta-kms-types.h
@@ -59,7 +59,7 @@ typedef enum _MetaKmsDeviceFlag
   META_KMS_DEVICE_FLAG_NONE = 0,
   META_KMS_DEVICE_FLAG_BOOT_VGA = 1 << 0,
   META_KMS_DEVICE_FLAG_PLATFORM_DEVICE = 1 << 1,
-  META_KMS_DEVICE_FLAG_REQUIRES_MODIFIERS = 1 << 2,
+  META_KMS_DEVICE_FLAG_DISABLE_MODIFIERS = 1 << 2,
   META_KMS_DEVICE_FLAG_PREFERRED_PRIMARY = 1 << 3,
   META_KMS_DEVICE_FLAG_NO_MODE_SETTING = 1 << 4,
 } MetaKmsDeviceFlag;
diff --git a/src/backends/native/meta-renderer-native.c b/src/backends/native/meta-renderer-native.c
index f48db9ab8b..d00128d56c 100644
--- a/src/backends/native/meta-renderer-native.c
+++ b/src/backends/native/meta-renderer-native.c
@@ -1984,6 +1984,8 @@ meta_renderer_native_initable_init (GInitable     *initable,
   gpus = meta_backend_get_gpus (backend);
   if (gpus)
     {
+      const char *use_kms_modifiers_debug_env;
+
       for (l = gpus; l; l = l->next)
         {
           MetaGpuKms *gpu_kms = META_GPU_KMS (l->data);
@@ -1998,8 +2000,20 @@ meta_renderer_native_initable_init (GInitable     *initable,
       if (!renderer_native->primary_gpu_kms)
         return FALSE;
 
-      if (meta_gpu_kms_requires_modifiers (renderer_native->primary_gpu_kms))
-        renderer_native->use_modifiers = TRUE;
+      use_kms_modifiers_debug_env = g_getenv ("MUTTER_DEBUG_USE_KMS_MODIFIERS");
+      if (use_kms_modifiers_debug_env)
+        {
+          renderer_native->use_modifiers =
+            g_strcmp0 (use_kms_modifiers_debug_env, "1") == 0;
+        }
+      else
+        {
+          renderer_native->use_modifiers =
+            !meta_gpu_kms_disable_modifiers (renderer_native->primary_gpu_kms);
+        }
+
+      meta_topic (META_DEBUG_KMS, "Usage of KMS modifiers is %s",
+                  renderer_native->use_modifiers ? "enabled" : "disabled");
     }
   else
     {
diff --git a/src/backends/native/meta-udev.c b/src/backends/native/meta-udev.c
index 9a6bfe03ba..5d58d6b56f 100644
--- a/src/backends/native/meta-udev.c
+++ b/src/backends/native/meta-udev.c
@@ -75,7 +75,7 @@ meta_is_udev_device_boot_vga (GUdevDevice *device)
 }
 
 gboolean
-meta_is_udev_device_requires_modifiers (GUdevDevice *device)
+meta_is_udev_device_disable_modifiers (GUdevDevice *device)
 {
   g_autoptr (GUdevDevice) platform_device = NULL;
   const char * const * tags;
@@ -92,7 +92,7 @@ meta_is_udev_device_requires_modifiers (GUdevDevice *device)
   if (!tags)
     return FALSE;
 
-  return g_strv_contains (tags, "mutter-device-requires-kms-modifiers");
+  return g_strv_contains (tags, "mutter-device-disable-kms-modifiers");
 }
 
 gboolean
diff --git a/src/backends/native/meta-udev.h b/src/backends/native/meta-udev.h
index 453cce9a71..360e062133 100644
--- a/src/backends/native/meta-udev.h
+++ b/src/backends/native/meta-udev.h
@@ -32,7 +32,7 @@ gboolean meta_is_udev_device_platform_device (GUdevDevice *device);
 
 gboolean meta_is_udev_device_boot_vga (GUdevDevice *device);
 
-gboolean meta_is_udev_device_requires_modifiers (GUdevDevice *device);
+gboolean meta_is_udev_device_disable_modifiers (GUdevDevice *device);
 
 gboolean meta_is_udev_device_preferred_primary (GUdevDevice *device);