drm/amdgpu: Add stutter mode ctrl in module parameter

Enable stutter mode can save power in low DRAM use cases
including but not limited to productivity application use,
web browsing, and video playback.

Currently this feature is disabled by default.

Make bit 17 in module parameter amdgpu_pp_feature_mask
as stutter mode mask, so user can enable/disable this feature easily.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Rex Zhu <Rex.Zhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -122,7 +122,8 @@ uint amdgpu_pg_mask = 0xffffffff;
 uint amdgpu_sdma_phase_quantum = 32;
 char *amdgpu_disable_cu = NULL;
 char *amdgpu_virtual_display = NULL;
-uint amdgpu_pp_feature_mask = 0xffff3fff; /* gfxoff (bit 15) disabled by default */
+/* OverDrive(bit 14),gfxoff(bit 15),stutter mode(bit 17) disabled by default*/
+uint amdgpu_pp_feature_mask = 0xfffd3fff;
 int amdgpu_ngg = 0;
 int amdgpu_prim_buf_per_se = 0;
 int amdgpu_pos_buf_per_se = 0;

drivers/gpu/drm/amd/include/amd_shared.h

@@ -128,6 +128,7 @@ enum PP_FEATURE_MASK {
 	PP_OVERDRIVE_MASK = 0x4000,
 	PP_GFXOFF_MASK = 0x8000,
 	PP_ACG_MASK = 0x10000,
+	PP_STUTTER_MODE = 0x20000,
 };
 
 struct amd_ip_funcs {