drm/amdgpu: add S/G display parameter

commit bf0207e1727031798f300afa17f9bbeceac6da87 upstream.

Some users have reported flickerng with S/G display.  We've
tried extensively to reproduce and debug the issue on a wide
variety of platform configurations (DRAM bandwidth, etc.) and
a variety of monitors, but so far have not been able to.  We
disabled S/G display on a number of platforms to address this
but that leads to failure to pin framebuffers errors and
blank displays when there is memory pressure or no displays
at all on systems with limited carveout (e.g., Chromebooks).
Add a option to disable this as a debugging option as a
way for users to disable this, depending on their use case,
and for us to help debug this further.

v2: fix typo

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index c0e782a95e72efd34ee514c65b4ae00ae361c77e..e0f146ddc5562a8cb812b9974f09930d79a198a2 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -242,6 +242,7 @@ extern int amdgpu_num_kcq;
 
 #define AMDGPU_VCNFW_LOG_SIZE (32 * 1024)
 extern int amdgpu_vcnfw_log;
+extern int amdgpu_sg_display;
 
 #define AMDGPU_VM_MAX_NUM_CTX                  4096
 #define AMDGPU_SG_THRESHOLD                    (256*1024*1024)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 49a023f59b2fc67edc99b5310da5b0b553095331..6e5bc74846952d079044c1d4ab7ef6a3dc9f8ff2 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -185,6 +185,7 @@ int amdgpu_num_kcq = -1;
 int amdgpu_smartshift_bias;
 int amdgpu_use_xgmi_p2p = 1;
 int amdgpu_vcnfw_log;
+int amdgpu_sg_display = -1; /* auto */
 
 static void amdgpu_drv_delayed_reset_work_handler(struct work_struct *work);
 
@@ -929,6 +930,16 @@ module_param_named(num_kcq, amdgpu_num_kcq, int, 0444);
 MODULE_PARM_DESC(vcnfw_log, "Enable vcnfw log(0 = disable (default value), 1 = enable)");
 module_param_named(vcnfw_log, amdgpu_vcnfw_log, int, 0444);
 
+/**
+ * DOC: sg_display (int)
+ * Disable S/G (scatter/gather) display (i.e., display from system memory).
+ * This option is only relevant on APUs.  Set this option to 0 to disable
+ * S/G display if you experience flickering or other issues under memory
+ * pressure and report the issue.
+ */
+MODULE_PARM_DESC(sg_display, "S/G Display (-1 = auto (default), 0 = disable)");
+module_param_named(sg_display, amdgpu_sg_display, int, 0444);
+
 /**
  * DOC: smu_pptable_id (int)
  * Used to override pptable id. id = 0 use VBIOS pptable.

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 86e07cc1d3dcc5ce628873ba2102496b01df79d9..41dec9eb08f0db63089eb743ac4cd2ac45d644db 100644 (file)
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -1634,6 +1634,9 @@ 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)
                adev->mode_info.gpu_vm_support = true;