target/linux/bcm27xx/patches-5.10/950-0716-drm-gud-Add-async_flush-module-parameter.patch

   1 From e0eb7ca2dd07ca8878b67cc20e75f9d7e46d80f4 Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
   3 Date: Sat, 3 Jul 2021 16:13:21 +0200
   4 Subject: [PATCH] drm/gud: Add async_flush module parameter
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 [ drm-misc commit a0356899ebe8ecde0da9c5685cc47154db973a5e ]
  10
  11 Provide a way for userspace to choose synchronous flushing/pageflips.
  12 This helps save CPU and power.
  13
  14 It is also useful for test scripts since userspace can know when a flush
  15 has happended and wait before doing the next visual test.
  16
  17 Cc: Linus Walleij <linus.walleij@linaro.org>
  18 Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
  19 Reviewed-by: Peter Stuge <peter@stuge.se>
  20 Link: https://patchwork.freedesktop.org/patch/msgid/20210703141321.35494-2-noralf@tronnes.org
  21 ---
  22  drivers/gpu/drm/gud/gud_pipe.c | 15 +++++++++++++++
  23  1 file changed, 15 insertions(+)
  24
  25 --- a/drivers/gpu/drm/gud/gud_pipe.c
  26 +++ b/drivers/gpu/drm/gud/gud_pipe.c
  27 @@ -24,6 +24,19 @@
  28  #include "gud_internal.h"
  29
  30  /*
  31 + * Some userspace rendering loops runs all displays in the same loop.
  32 + * This means that a fast display will have to wait for a slow one.
  33 + * For this reason gud does flushing asynchronous by default.
  34 + * The down side is that in e.g. a single display setup userspace thinks
  35 + * the display is insanely fast since the driver reports back immediately
  36 + * that the flush/pageflip is done. This wastes CPU and power.
  37 + * Such users might want to set this module parameter to false.
  38 + */
  39 +static bool gud_async_flush = true;
  40 +module_param_named(async_flush, gud_async_flush, bool, 0644);
  41 +MODULE_PARM_DESC(async_flush, "Enable asynchronous flushing [default=true]");
  42 +
  43 +/*
  44   * FIXME: The driver is probably broken on Big Endian machines.
  45   * See discussion:
  46   * https://lore.kernel.org/dri-devel/CAKb7UvihLX0hgBOP3VBG7O+atwZcUVCPVuBdfmDMpg0NjXe-cQ@mail.gmail.com/
  47 @@ -577,6 +590,8 @@ void gud_pipe_update(struct drm_simple_d
  48                 if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE)
  49                         drm_rect_init(&damage, 0, 0, fb->width, fb->height);
  50                 gud_fb_queue_damage(gdrm, fb, &damage);
  51 +               if (!gud_async_flush)
  52 +                       flush_work(&gdrm->work);
  53         }
  54
  55         if (!crtc->state->enable)