[PATCH v13 0/2] drm: add kms driver for loongson display controller

From: Sui Jingfeng
Date: Mon May 15 2023 - 11:57:53 EST

Loongson display controller IP has been integrated in both Loongson north
bridge chipset(ls7a1000/ls7a2000) and Loongson SoCs(ls2k1000/ls2k2000), it
has been even included in Loongson self-made BMC products.

This display controller is a PCI device. It has two display pipes and each
display pipe support a primary plane and a cursor plane. For the DC in the
ls7a1000 and ls2k1000, each display pipe has a DVO output interface which
provide RGB888 signals, vertical & horizontal synchronisations and pixel
clock. Each CRTC is able to support 1920x1080@60Hz, the maximum resolution
of each display pipe is 2048x2048 according to the hardware spec.

For the DC in LS7A2000, each display pipe is equipped with a built-in HDMI
encoder which is compliant with the HDMI 1.4 specification, thus it support
3840x2160@30Hz. The first display pipe is also equipped with a transparent
vga encoder which is parallel with the HDMI encoder. The DC in LS7A2000 is
more complete compare with the one in old chips, besides above feature, it
has two hardware cursors, two hardware vblank counter and two scanout
position recorders unit. It also support tiled framebuffer format which
can be scanout the tiled framebuffer rendered by the LoongGPU directly.

v1 -> v2:
1) Use hpd status reg when polling for ls7a2000
2) Fix all warnings emerged when compile with W=1

v2 -> v3:
1) Add COMPILE_TEST in Kconfig and make the driver off by default
2) Alphabetical sorting headers (Thomas)
3) Untangle register access functions as much as possible (Thomas)
4) Switch to TTM based memory manager and prefer cached mapping
for Loongson SoC (Thomas)
5) Add chip id detection method, now all models are distinguishable.
6) Revise builtin HDMI phy driver, nearly all main stream mode
below 4K@30Hz is tested, this driver supported these mode very
well including clone display mode and extend display mode.

v3 -> v4:
1) Quickly fix a small mistake.

v4 -> v5:
1) Drop potential support for Loongson 2K series SoC temporary,
this part should be resend with the DT binding patch in the future.
2) Add per display pipe debugfs support to the builtin HDMI encoder.
3) Rewrite atomic_update() for hardware cursors plane(Thomas)
4) Rewrite encoder and connector initialization part, untangle it
according to the chip(Thomas).

v5 -> v6:
1) Remove stray code which didn't get used, say lsdc_of_get_reserved_ram
2) Fix all typos I could found, make sentences and code more readable
3) Untangle lsdc_hdmi*_connector_detect() function according to the pipe
4) After a serious consideration, we rename this driver as loongson.
Because we also have drivers toward the LoongGPU IP in LS7A2000 and
LS2K2000. Besides, there are also drivers about the external encoder,
HDMI audio driver and vbios support etc. This patch only provide DC
driver part, my teammate Li Yi believe that loongson will be more
suitable for loongson graphics than lsdc in the long run.

loongson.ko = LSDC + LoongGPU + encoders driver + vbios/DT ...

v6 -> v7:
1) Add prime support, self-sharing is works. sharing buffer with etnaviv
is also tested, and its works with limitation.
2) Implement buffer objects tracking with list_head.
3) S3(sleep to RAM) is tested on ls3a5000+ls7a2000 evb and it works.
4) Rewrite lsdc_bo_move, since ttm core stop allocating resources
during BO creation. Patch V1 ~ V6 of this series no longer works
on latest kernel. Thus, we send V7 to revival them.

v7 -> v8:
1) Zero a compile warnnings on 32-bit platform, compile with W=1
2) Revise lsdc_bo_gpu_offset() and minor cleanup
3) Pageflip tested on the virtual terminal with following commands

modetest -M loongson -s 32:1920x1080 -v
modetest -M loongson -s 34:1920x1080 -v -F tiles

It works like a charm, when running pageflip test with dual screnn
configuration, another two additional bo created by the modetest
emerged, VRAM usage up to 40+MB, well we have at least 64MB, still

# cat bos

bo[0000]: size: 8112kB VRAM
bo[0001]: size: 16kB VRAM
bo[0002]: size: 16kB VRAM
bo[0003]: size: 16208kB VRAM
bo[0004]: size: 8112kB VRAM
bo[0005]: size: 8112kB VRAM

v8 -> v9:
1) Select I2C and I2C_ALGOBIT in Kconfig and should depend on MMU.
2) Using pci_get_domain_bus_and_slot to get the GPU device.
3) Other minor improvements.

Those patches are tested on ls3a5000 + ls7a1000 CRB, ls3a5000 + ls7a2000
evb, and lemote a1901 board(ls3a4000 + ls7a1000). On loongson mips CPU,
the write combine support should be enabled, to get a decent performance
for writing framebuffer data to the VRAM.

v9 -> v10:
1) Revise lsdc_drm_freeze() to implement S3 completely and correctly.
I suddenly realized that pinned buffer can not move and VRAM lost
power when sleep to RAM. Thus, the data in the buffer who is pinned
in VRAM will get lost when resume. Yet it's not big problem because
we are software rendering solution which relay on the CPU update the
front framebuffer. We can see the garbage data when resume from S3,
but the screen will show correct image as I move the cursor. This is
due to the cpu repaint. v10 of this patch make S3 perfect by unpin
all of BOs in VRAM, evict them all to system RAM.

v10 -> v11:
1) On double screen case, the single giant framebuffer is referenced by
two GEM object, hence, it will be pinned by prepare_fb() at lease two
times. This cause its pin count > 1. V10 of this patch only unpin VRAM
BOs once when suspend, which is not correct on double screen case. V11
of this patch unpin BOs until its pin count reach to zero when suspend.
Then, we make the S3 support complete finally. With v11, I can't see
any garbage data after resume. Tested on both ls7a1000 and ls7a2000
platform, with single screen and double screen configuration.
2) Fix vblank wait timeout when disable CRTC.
3) Test against IGT, at least fbdev test and kms_flip test passed.
4) Rewrite pixel PLL update function, magic numbers eliminated (Emil)
5) Drop a few common hardware features description in lsdc_desc (Emil)
6) Drop lsdc_mode_config_mode_valid(), instead add restrictions in dumb
create function. (Emil)
7) Untangle the ls7a1000 case and ls7a2000 case completely (Thomas)

v11 -> v12:

v12 -> v13:
1) Add benchmark to figure out the bandwidth of the hardware platform.
# cd /sys/kernel/debug/dri/0/
# cat benchmark

2) VRAM is filled with garbage data if uninitialized, add a buffer
clearing procedure, clear it on the BO creation time.
3) Update copyrights and adjust coding style (Huacai)

Sui Jingfeng (2):
drm: add kms driver for loongson display controller
MAINTAINERS: add maintainers for DRM LOONGSON driver

drivers/gpu/drm/Kconfig | 2 +
drivers/gpu/drm/Makefile | 1 +
drivers/gpu/drm/loongson/Kconfig | 17 +
drivers/gpu/drm/loongson/Makefile | 21 +
drivers/gpu/drm/loongson/ls7a1000_outputs.c | 161 +++
drivers/gpu/drm/loongson/ls7a2000_outputs.c | 531 +++++++++
drivers/gpu/drm/loongson/lsdc_benchmark.c | 132 +++
drivers/gpu/drm/loongson/lsdc_benchmark.h | 13 +
drivers/gpu/drm/loongson/lsdc_crtc.c | 1068 +++++++++++++++++++
drivers/gpu/drm/loongson/lsdc_debugfs.c | 91 ++
drivers/gpu/drm/loongson/lsdc_device.c | 104 ++
drivers/gpu/drm/loongson/lsdc_drv.c | 484 +++++++++
drivers/gpu/drm/loongson/lsdc_drv.h | 452 ++++++++
drivers/gpu/drm/loongson/lsdc_gem.c | 324 ++++++
drivers/gpu/drm/loongson/lsdc_gem.h | 37 +
drivers/gpu/drm/loongson/lsdc_gfxpll.c | 199 ++++
drivers/gpu/drm/loongson/lsdc_gfxpll.h | 52 +
drivers/gpu/drm/loongson/lsdc_i2c.c | 179 ++++
drivers/gpu/drm/loongson/lsdc_i2c.h | 29 +
drivers/gpu/drm/loongson/lsdc_irq.c | 81 ++
drivers/gpu/drm/loongson/lsdc_irq.h | 16 +
drivers/gpu/drm/loongson/lsdc_output.h | 21 +
drivers/gpu/drm/loongson/lsdc_pixpll.c | 481 +++++++++
drivers/gpu/drm/loongson/lsdc_pixpll.h | 86 ++
drivers/gpu/drm/loongson/lsdc_plane.c | 639 +++++++++++
drivers/gpu/drm/loongson/lsdc_probe.c | 56 +
drivers/gpu/drm/loongson/lsdc_probe.h | 12 +
drivers/gpu/drm/loongson/lsdc_regs.h | 400 +++++++
drivers/gpu/drm/loongson/lsdc_ttm.c | 610 +++++++++++
drivers/gpu/drm/loongson/lsdc_ttm.h | 99 ++
31 files changed, 6406 insertions(+)
create mode 100644 drivers/gpu/drm/loongson/Kconfig
create mode 100644 drivers/gpu/drm/loongson/Makefile
create mode 100644 drivers/gpu/drm/loongson/ls7a1000_outputs.c
create mode 100644 drivers/gpu/drm/loongson/ls7a2000_outputs.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_benchmark.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_benchmark.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_crtc.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_debugfs.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_device.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_drv.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_drv.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_gem.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_gem.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_gfxpll.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_gfxpll.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_i2c.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_i2c.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_irq.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_irq.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_output.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_pixpll.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_pixpll.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_plane.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_probe.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_probe.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_regs.h
create mode 100644 drivers/gpu/drm/loongson/lsdc_ttm.c
create mode 100644 drivers/gpu/drm/loongson/lsdc_ttm.h