Commit 5fd953a3 authored by Rodrigo Siqueira's avatar Rodrigo Siqueira Committed by Alex Deucher
Browse files

drm/amd/display: Add Freesync video documentation 



Recently, we added support for an experimental feature named Freesync
video; for more details on that, refer to:

commit 6f59f229 ("drm/amd/display: Skip modeset for front porch change")
commit d10cd527 ("drm/amd/display: Add freesync video modes based on preferred modes")
commit 0eb1af2e ("drm/amd/display: Add module parameter for freesync video mode")

Nevertheless, we did not document it in detail in our driver. This
commit introduces a kernel-doc and expands the module parameter
description.

Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: default avatarRodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Reviewed by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 26c0504a

Documentation/gpu/amdgpu-dc.rst

+6 −0
Original line number Diff line number Diff line
@@ -66,3 +66,9 @@ Display Core 
============



**WIP**



FreeSync Video

--------------



.. kernel-doc:: drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

   :doc: FreeSync Video

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

+17 −2
Original line number Diff line number Diff line
@@ -837,8 +837,23 @@ module_param_named(tmz, amdgpu_tmz, int, 0444); 


/**

 * DOC: freesync_video (uint)

 * Enabled the optimization to adjust front porch timing to achieve seamless mode change experience

 * when setting a freesync supported mode for which full modeset is not needed.

 * Enable the optimization to adjust front porch timing to achieve seamless

 * mode change experience when setting a freesync supported mode for which full

 * modeset is not needed.

 *

 * The Display Core will add a set of modes derived from the base FreeSync

 * video mode into the corresponding connector's mode list based on commonly

 * used refresh rates and VRR range of the connected display, when users enable

 * this feature. From the userspace perspective, they can see a seamless mode

 * change experience when the change between different refresh rates under the

 * same resolution. Additionally, userspace applications such as Video playback

 * can read this modeset list and change the refresh rate based on the video

 * frame rate. Finally, the userspace can also derive an appropriate mode for a

 * particular refresh rate based on the FreeSync Mode and add it to the

 * connector's mode list.

 *

 * Note: This is an experimental feature.

 *

 * The default value: 0 (off).

 */

MODULE_PARM_DESC(

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

+30 −0
Original line number Diff line number Diff line
@@ -5646,6 +5646,36 @@ static void apply_dsc_policy_for_stream(struct amdgpu_dm_connector *aconnector, 
}

#endif



/**

 * DOC: FreeSync Video

 *

 * When a userspace application wants to play a video, the content follows a

 * standard format definition that usually specifies the FPS for that format.

 * The below list illustrates some video format and the expected FPS,

 * respectively:

 *

 * - TV/NTSC (23.976 FPS)

 * - Cinema (24 FPS)

 * - TV/PAL (25 FPS)

 * - TV/NTSC (29.97 FPS)

 * - TV/NTSC (30 FPS)

 * - Cinema HFR (48 FPS)

 * - TV/PAL (50 FPS)

 * - Commonly used (60 FPS)

 * - Multiples of 24 (48,72,96 FPS)

 *

 * The list of standards video format is not huge and can be added to the

 * connector modeset list beforehand. With that, userspace can leverage

 * FreeSync to extends the front porch in order to attain the target refresh

 * rate. Such a switch will happen seamlessly, without screen blanking or

 * reprogramming of the output in any other way. If the userspace requests a

 * modesetting change compatible with FreeSync modes that only differ in the

 * refresh rate, DC will skip the full update and avoid blink during the

 * transition. For example, the video player can change the modesetting from

 * 60Hz to 30Hz for playing TV/NTSC content when it goes full screen without

 * causing any display blink. This same concept can be applied to a mode

 * setting change.

 */

static struct drm_display_mode *

get_highest_refresh_rate_mode(struct amdgpu_dm_connector *aconnector,

			  bool use_probed_modes)