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drm/gud: Add async_flush module parameter 

Provide a way for userspace to choose synchronous flushing/pageflips.
This helps save CPU and power.

It is also useful for test scripts since userspace can know when a flush
has happended and wait before doing the next visual test.

Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Peter Stuge <peter@stuge.se>
Link: https://patchwork.freedesktop.org/patch/msgid/20210703141321.35494-2-noralf@tronnes.org
pull/78/merge
Noralf Trønnes 2021-07-03 16:13:21 +02:00
parent b3f4ef6693
commit a0356899eb
1 changed files with 15 additions and 0 deletions
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15
drivers/gpu/drm/gud/gud_pipe.c
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@ -23,6 +23,19 @@
#include "gud_internal.h"
/*
* Some userspace rendering loops runs all displays in the same loop.
* This means that a fast display will have to wait for a slow one.
* For this reason gud does flushing asynchronous by default.
* The down side is that in e.g. a single display setup userspace thinks
* the display is insanely fast since the driver reports back immediately
* that the flush/pageflip is done. This wastes CPU and power.
* Such users might want to set this module parameter to false.
*/
static bool gud_async_flush = true;
module_param_named(async_flush, gud_async_flush, bool, 0644);
MODULE_PARM_DESC(async_flush, "Enable asynchronous flushing [default=true]");
/*
* FIXME: The driver is probably broken on Big Endian machines.
* See discussion:
@ -578,6 +591,8 @@ void gud_pipe_update(struct drm_simple_display_pipe *pipe,
if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
drm_rect_init(&damage, 0, 0, fb->width, fb->height);
gud_fb_queue_damage(gdrm, fb, &damage);
if (!gud_async_flush)
flush_work(&gdrm->work);
}
if (!crtc->state->enable)