drm/amdgpu: Add use_xgmi_p2p module parameter

This parameter controls xGMI p2p communication, which is enabled by
default. However, it can be disabled by setting it to 0. In case xGMI
p2p is disabled in a dGPU, PCIe p2p interface will be used instead.
This parameter is ignored in GPUs that do not support xGMI
p2p configuration.

Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Acked-by: Luben Tuikov <luben.tuikov@amd.com>
Acked-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

@@ -211,6 +211,7 @@ extern int amdgpu_mes;
 extern int amdgpu_noretry;
 extern int amdgpu_force_asic_type;
 extern int amdgpu_smartshift_bias;
+extern int amdgpu_use_xgmi_p2p;
 #ifdef CONFIG_HSA_AMD
 extern int sched_policy;
 extern bool debug_evictions;

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

@@ -176,6 +176,7 @@ int amdgpu_tmz = -1; /* auto */
 int amdgpu_reset_method = -1; /* auto */
 int amdgpu_num_kcq = -1;
 int amdgpu_smartshift_bias;
+int amdgpu_use_xgmi_p2p = 1;
 
 static void amdgpu_drv_delayed_reset_work_handler(struct work_struct *work);
 
@@ -651,6 +652,13 @@ MODULE_PARM_DESC(force_asic_type,
 	"A non negative value used to specify the asic type for all supported GPUs");
 module_param_named(force_asic_type, amdgpu_force_asic_type, int, 0444);
 
+/**
+ * DOC: use_xgmi_p2p (int)
+ * Enables/disables XGMI P2P interface (0 = disable, 1 = enable).
+ */
+MODULE_PARM_DESC(use_xgmi_p2p,
+	"Enable XGMI P2P interface (0 = disable; 1 = enable (default))");
+module_param_named(use_xgmi_p2p, amdgpu_use_xgmi_p2p, int, 0444);
 
 
 #ifdef CONFIG_HSA_AMD

drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h

@@ -66,7 +66,8 @@ uint64_t amdgpu_xgmi_get_relative_phy_addr(struct amdgpu_device *adev,
 static inline bool amdgpu_xgmi_same_hive(struct amdgpu_device *adev,
 		struct amdgpu_device *bo_adev)
 {
-	return (adev != bo_adev &&
+	return (amdgpu_use_xgmi_p2p &&
+		adev != bo_adev &&
 		adev->gmc.xgmi.hive_id &&
 		adev->gmc.xgmi.hive_id == bo_adev->gmc.xgmi.hive_id);
 }