From: jsg <jsg@openbsd.org>
Date: Thu, 17 Aug 2023 03:43:42 +0000 (+0000)
Subject: drm/amd: Disable S/G for APUs when 64GB or more host memory
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=81d480980bcbfb8fdd8bbcbec83a5b370fc9b60e;p=openbsd

drm/amd: Disable S/G for APUs when 64GB or more host memory

From Mario Limonciello
10347b115da1029f4a25b69129294b3854144d6a in linux-6.1.y/6.1.46
08fffa74d9772d9538338be3f304006c94dde6f0 in mainline linux
---

diff --git a/sys/dev/pci/drm/amd/amdgpu/amdgpu.h b/sys/dev/pci/drm/amd/amdgpu/amdgpu.h
index 7bac1c1336f..b15b9dc227a 100644
--- a/sys/dev/pci/drm/amd/amdgpu/amdgpu.h
+++ b/sys/dev/pci/drm/amd/amdgpu/amdgpu.h
@@ -1292,6 +1292,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 void amdgpu_device_pci_config_reset(struct amdgpu_device *adev);
 int amdgpu_device_pci_reset(struct amdgpu_device *adev);
 bool amdgpu_device_need_post(struct amdgpu_device *adev);
+bool amdgpu_sg_display_supported(struct amdgpu_device *adev);
 bool amdgpu_device_pcie_dynamic_switching_supported(void);
 bool amdgpu_device_should_use_aspm(struct amdgpu_device *adev);
 bool amdgpu_device_aspm_support_quirk(void);
diff --git a/sys/dev/pci/drm/amd/amdgpu/amdgpu_device.c b/sys/dev/pci/drm/amd/amdgpu/amdgpu_device.c
index b48d639d861..73fa47c34f7 100644
--- a/sys/dev/pci/drm/amd/amdgpu/amdgpu_device.c
+++ b/sys/dev/pci/drm/amd/amdgpu/amdgpu_device.c
@@ -1351,6 +1351,32 @@ bool amdgpu_device_need_post(struct amdgpu_device *adev)
 	return true;
 }
 
+/*
+ * On APUs with >= 64GB white flickering has been observed w/ SG enabled.
+ * Disable S/G on such systems until we have a proper fix.
+ * https://gitlab.freedesktop.org/drm/amd/-/issues/2354
+ * https://gitlab.freedesktop.org/drm/amd/-/issues/2735
+ */
+bool amdgpu_sg_display_supported(struct amdgpu_device *adev)
+{
+	switch (amdgpu_sg_display) {
+	case -1:
+		break;
+	case 0:
+		return false;
+	case 1:
+		return true;
+	default:
+		return false;
+	}
+	if ((totalram_pages() << (PAGE_SHIFT - 10)) +
+	    (adev->gmc.real_vram_size / 1024) >= 64000000) {
+		DRM_WARN("Disabling S/G due to >=64GB RAM\n");
+		return false;
+	}
+	return true;
+}
+
 /*
  * Intel hosts such as Raptor Lake and Sapphire Rapids don't support dynamic
  * speed switching. Until we have confirmation from Intel that a specific host
diff --git a/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index d9e78102880..25febd19d2f 100644
--- a/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/sys/dev/pci/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1636,9 +1636,8 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 		}
 		break;
 	}
-	if (init_data.flags.gpu_vm_support &&
-	    (amdgpu_sg_display == 0))
-		init_data.flags.gpu_vm_support = false;
+	if (init_data.flags.gpu_vm_support)
+		init_data.flags.gpu_vm_support = amdgpu_sg_display_supported(adev);
 
 	if (init_data.flags.gpu_vm_support)
 		adev->mode_info.gpu_vm_support = true;