[PATCH v5 00/13] Add video damage tracking

[Alper Nebi Yasak]

This is a rebase of Alexander Graf's video damage tracking series, with
some tests and other changes. The original cover letter is as follows:

> This patch set speeds up graphics output on ARM by a factor of 60x.
>
> On most ARM SBCs, we keep the frame buffer in DRAM and map it as cached,
> but need it accessible by the display controller which reads directly
> from a later point of consistency. Hence, we flush the frame buffer to
> DRAM on every change. The full frame buffer.
>
> Unfortunately, with the advent of 4k displays, we are seeing frame buffers
> that can take a while to flush out. This was reported by Da Xue with grub,
> which happily print 1000s of spaces on the screen to draw a menu. Every
> printed space triggers a cache flush.
>
> This patch set implements the easiest mitigation against this problem:
> Damage tracking. We remember the lowest common denominator region that was
> touched since the last video_sync() call and only flush that. The most
> typical writer to the frame buffer is the video console, which always
> writes rectangles of characters on the screen and syncs afterwards.
>
> With this patch set applied, we reduce drawing a large grub menu (with
> serial console attached for size information) on an RK3399-ROC system
> at 1440p from 55 seconds to less than 1 second.
>
> Version 2 also implements VIDEO_COPY using this mechanism, reducing its
> overhead compared to before as well. So even x86 systems should be faster
> with this now :).
>
>
> Alternatives considered:
>
>   1) Lazy sync - Sandbox does this. It only calls video_sync(true) ever
>      so often. We are missing timers to do this generically.
>
>   2) Double buffering - We could try to identify whether anything changed
>      at all and only draw to the FB if it did. That would require
>      maintaining a second buffer that we need to scan.
>
>   3) Text buffer - Maintain a buffer of all text printed on the screen with
>      respective location. Don't write if the old and new character are
>      identical. This would limit applicability to text only and is an
>      optimization on top of this patch set.
>
>   4) Hash screen lines - Create a hash (sha256?) over every line when it
>      changes. Only flush when it does. I'm not sure if this would waste
>      more time, memory and cache than the current approach. It would make
>      full screen updates much more expensive.

Changes in v5:
- Add patch "video: test: Split copy frame buffer check into a function"
- Add patch "video: test: Support checking copy frame buffer contents"
- Add patch "video: test: Test partial updates of hardware frame buffer"
- Use xstart, ystart, xend, yend as names for damage region
- Document damage struct and fields in struct video_priv comment
- Return void from video_damage()
- Fix undeclared priv error in video_sync()
- Drop unused headers from video-uclass.c
- Use IS_ENABLED() instead of CONFIG_IS_ENABLED()
- Call video_damage() also in video_fill_part()
- Use met->baseline instead of priv->baseline
- Use fontdata->height/width instead of VIDEO_FONT_HEIGHT/WIDTH
- Update console_rotate.c video_damage() calls to pass video tests
- Remove mention about not having minimal damage for console_rotate.c
- Add patch "video: test: Test video damage tracking via vidconsole"
- Document new vdev field in struct efi_gop_obj comment
- Remove video_sync_copy() also from video_fill(), video_fill_part()
- Fix memmove() calls by removing the extra dev argument
- Call video_sync() before checking copy_fb in video tests
- Imply VIDEO_DAMAGE for video drivers instead of selecting it
- Imply VIDEO_DAMAGE also for VIDEO_TIDSS

v4: https://lore.kernel.org/all/20230103215004.22646-1-agraf@csgraf.de/

Changes in v4:
- Move damage clear to patch "dm: video: Add damage tracking API"
- Simplify first damage logic
- Remove VIDEO_DAMAGE default for ARM
- Skip damage on EfiBltVideoToBltBuffer
- Add patch "video: Always compile cache flushing code"
- Add patch "video: Enable VIDEO_DAMAGE for drivers that need it"

v3: https://lore.kernel.org/all/20221230195828.88134-1-agraf@csgraf.de/

Changes in v3:
- Adapt to always assume DM is used
- Adapt to always assume DM is used
- Make VIDEO_COPY always select VIDEO_DAMAGE

v2: https://lore.kernel.org/all/20220609225921.62462-1-agraf@csgraf.de/

Changes in v2:
- Remove ifdefs
- Fix ranges in truetype target
- Limit rotate to necessary damage
- Remove ifdefs from gop
- Fix dcache range; we were flushing too much before
- Add patch "video: Use VIDEO_DAMAGE for VIDEO_COPY"

v1: https://lore.kernel.org/all/20220606234336.5021-1-agraf@csgraf.de/

Alexander Graf (9):
  dm: video: Add damage tracking API
  dm: video: Add damage notification on display fills
  vidconsole: Add damage notifications to all vidconsole drivers
  video: Add damage notification on bmp display
  efi_loader: GOP: Add damage notification on BLT
  video: Only dcache flush damaged lines
  video: Use VIDEO_DAMAGE for VIDEO_COPY
  video: Always compile cache flushing code
  video: Enable VIDEO_DAMAGE for drivers that need it

Alper Nebi Yasak (4):
  video: test: Split copy frame buffer check into a function
  video: test: Support checking copy frame buffer contents
  video: test: Test partial updates of hardware frame buffer
  video: test: Test video damage tracking via vidconsole

 arch/arm/mach-omap2/omap3/Kconfig |   1 +
 arch/arm/mach-sunxi/Kconfig       |   1 +
 drivers/video/Kconfig             |  26 +++
 drivers/video/console_normal.c    |  27 ++--
 drivers/video/console_rotate.c    |  94 +++++++----
 drivers/video/console_truetype.c  |  37 +++--
 drivers/video/exynos/Kconfig      |   1 +
 drivers/video/imx/Kconfig         |   1 +
 drivers/video/meson/Kconfig       |   1 +
 drivers/video/rockchip/Kconfig    |   1 +
 drivers/video/stm32/Kconfig       |   1 +
 drivers/video/tegra20/Kconfig     |   1 +
 drivers/video/tidss/Kconfig       |   1 +
 drivers/video/vidconsole-uclass.c |  16 --
 drivers/video/video-uclass.c      | 190 ++++++++++++----------
 drivers/video/video_bmp.c         |   7 +-
 include/video.h                   |  59 +++----
 include/video_console.h           |  52 ------
 lib/efi_loader/efi_gop.c          |   7 +
 test/dm/video.c                   | 256 ++++++++++++++++++++++++------
 20 files changed, 483 insertions(+), 297 deletions(-)


base-commit: 3881c9fbb7fdd98f6eae5cd33f7e9abe9455a585
-- 
2.40.1