[PATCH] drm/amdgpu: add force_sg_display module parameter

[Alex Deucher <alexander.deucher@amd.com>]

Add a module parameter to force sg (scatter/gather) display
on APUs.  Normally we allow displays in both VRAM and GTT,
but this option forces displays into GTT so we can explicitly
test more scenarios with GTT.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    | 12 ++++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c |  4 ++++
 3 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 872450a3a164..73d0a0807138 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -244,6 +244,8 @@ extern int amdgpu_num_kcq;
 #define AMDGPU_VCNFW_LOG_SIZE (32 * 1024)
 extern int amdgpu_vcnfw_log;
 
+extern int amdgpu_force_sg_display;
+
 #define AMDGPU_VM_MAX_NUM_CTX			4096
 #define AMDGPU_SG_THRESHOLD			(256*1024*1024)
 #define AMDGPU_DEFAULT_GTT_SIZE_MB		3072ULL /* 3GB by default */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index a75dba2caeca..bc0eaf2330f2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -942,6 +942,18 @@ MODULE_PARM_DESC(smu_pptable_id,
 	"specify pptable id to be used (-1 = auto(default) value, 0 = use pptable from vbios, > 0 = soft pptable id)");
 module_param_named(smu_pptable_id, amdgpu_smu_pptable_id, int, 0444);
 
+/**
+ * DOC: force_sg_display (int)
+ * Force display buffers into GTT (scatter/gather) memory for APUs.
+ * This is used to force GTT only for displays rather than displaying from
+ * either VRAM (carve out) or GTT.
+ *
+ * Defaults to 0, or disabled.
+ */
+int amdgpu_force_sg_display;
+MODULE_PARM_DESC(force_sg_display, "Force S/G display (0 = off (default), 1 = force display to use GTT) ");
+module_param_named(force_sg_display, amdgpu_force_sg_display, int, 0444);
+
 /* These devices are not supported by amdgpu.
  * They are supported by the mach64, r128, radeon drivers
  */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index 2d237f3d3a2e..78dc5d63a6dd 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -1515,6 +1515,10 @@ uint32_t amdgpu_bo_get_preferred_domain(struct amdgpu_device *adev,
 		if (adev->gmc.real_vram_size <= AMDGPU_SG_THRESHOLD)
 			domain = AMDGPU_GEM_DOMAIN_GTT;
 	}
+	if (amdgpu_force_sg_display &&
+	    (adev->asic_type >= CHIP_CARRIZO) &&
+	    (adev->flags & AMD_IS_APU))
+		domain = AMDGPU_GEM_DOMAIN_GTT;
 	return domain;
 }
 
-- 
2.39.0