drm/amdgpu: Add module param to control SI support

If AMDGPU supports SI, add a module parameter to control SI
support. It's off by default in AMDGPU as long as SI suppost is
experimental, while it is on by default in radeon.
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Michel Dänzer <michel.daenzer@amd.com>

[ Michel Dänzer: Squash in amdgpu_si_support initialization fix ]
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -115,6 +115,9 @@ extern int amdgpu_param_buf_per_se;
 extern int amdgpu_job_hang_limit;
 extern int amdgpu_lbpw;
 
+#ifdef CONFIG_DRM_AMDGPU_SI
+extern int amdgpu_si_support;
+#endif
 #ifdef CONFIG_DRM_AMDGPU_CIK
 extern int amdgpu_cik_support;
 #endif

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

@@ -242,6 +242,12 @@ module_param_named(job_hang_limit, amdgpu_job_hang_limit, int ,0444);
 MODULE_PARM_DESC(lbpw, "Load Balancing Per Watt (LBPW) support (1 = enable, 0 = disable, -1 = auto)");
 module_param_named(lbpw, amdgpu_lbpw, int, 0444);
 
+#ifdef CONFIG_DRM_AMDGPU_SI
+int amdgpu_si_support = 0;
+MODULE_PARM_DESC(si_support, "SI support (1 = enabled, 0 = disabled (default))");
+module_param_named(si_support, amdgpu_si_support, int, 0444);
+#endif
+
 #ifdef CONFIG_DRM_AMDGPU_CIK
 int amdgpu_cik_support = 1;
 MODULE_PARM_DESC(cik_support, "CIK support (1 = enabled (default), 0 = disabled)");

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

@@ -87,6 +87,23 @@ int amdgpu_driver_load_kms(struct drm_device *dev, unsigned long flags)
 	struct amdgpu_device *adev;
 	int r, acpi_status;
 
+#ifdef CONFIG_DRM_AMDGPU_SI
+	if (!amdgpu_si_support) {
+		switch (flags & AMD_ASIC_MASK) {
+		case CHIP_TAHITI:
+		case CHIP_PITCAIRN:
+		case CHIP_VERDE:
+		case CHIP_OLAND:
+		case CHIP_HAINAN:
+			dev_info(dev->dev,
+				 "SI support provided by radeon.\n");
+			dev_info(dev->dev,
+		"Use radeon.si_support=0 amdgpu.si_support=1 to override.\n"
+				);
+			return -ENODEV;
+		}
+	}
+#endif
 #ifdef CONFIG_DRM_AMDGPU_CIK
 	if (!amdgpu_cik_support) {
 		switch (flags & AMD_ASIC_MASK) {