[PATCH v9 0/4] drm/lsdc: add drm driver for loongson display controller

[Sui Jingfeng]

There is a display controller in loongson's LS2K1000 SoC and LS7A1000
bridge chip, it is a PCI device in those chips. It has two display
pipes but with only one hardware cursor. Each way has a DVO interface
which provide RGB888 signals, vertical & horizontal synchronisations,
data enable and the pixel clock. Each CRTC is able to scanout from
1920x1080 resolution at 60Hz. The maxmium resolution is 2048x2048
according to the hardware spec. Loongson display controllers are simple
which require scanout buffers to be physically contiguous.

For LS7A1000/LS7A2000 bridge chip, the DC is equipped with a dedicated
video ram which is typically 64MB or more. In this case, VRAM helper
based driver is intend to be used. While LS2K1000 is a SoC, only system
memory is available. Therefore CMA helper based driver is intend to be
used. It is possible to use VRAM helper based solution by carving out
part of system memory as VRAM though.

For LS7A1000, there are 4 dedicated GPIOs whose control register is
located at the DC register space, They are used to emulate two way i2c.
One for DVO0, another for DVO1. LS2K1000 and LS2K0500 SoC don't have such
GPIO hardwared, they grab i2c adapter from other module, either general
purpose GPIO emulated i2c or hardware i2c adapter.

    +------+            +-----------------------------------+
    | DDR4 |            |  +-------------------+            |
    +------+            |  | PCIe Root complex |   LS7A1000 |
       || MC0           |  +--++---------++----+            |
  +----------+  HT 3.0  |     ||         ||                 |
  | LS3A4000 |<-------->| +---++---+  +--++--+    +---------+   +------+
  |   CPU    |<-------->| | GC1000 |  | LSDC |<-->| DDR3 MC |<->| VRAM |
  +----------+          | +--------+  +-+--+-+    +---------+   +------+
       || MC1           +---------------|--|----------------+
    +------+                            |  |
    | DDR4 |          +-------+   DVO0  |  |  DVO1   +------+
    +------+   VGA <--|ADV7125|<--------+  +-------->|TFP410|--> DVI/HDMI
                      +-------+                      +------+

The above picture give a simple usage of LS7A1000, note that the encoder
is not necessary adv7125 or tfp410, other candicate encoders can be
ch7034b, sil9022 and ite66121 lt8618 etc.

v2: fixup warnings reported by kernel test robot

v3: fix more grammar mistakes in Kconfig reported by Randy Dunlap and give
    more details about lsdc.

v4:
   1) Add dts required and explain why device tree is required.
   2) Give more description about lsdc and vram helper base driver.
   3) Fix warnings reported by kernel test robot.
   4) Introduce stride_alignment member into struct lsdc_chip_desc, the
      stride alignment is 256 bytes for ls7a1000, ls2k1000 and ls2k0500.
      But ls7a2000 improve it to 32 bytes, for extend the support for the
      device on coming.

v5:
   1) using writel and readl replace writeq and readq, to fix kernel test
      robot report build error on other archtecture
   2) set default fb format to XRGB8888 at crtc reset time.
   3) fix typos.

v6:
   1) Explain why we are not switch to drm dridge subsystem on ls2k1000.
   2) Explain why tiny drm driver is not suitable for us.
   3) Give a short description of the trival dirty uppdate implement based
      on CMA helper.
   4) code clean up

v7:
   1) Remove select I2C_GPIO and I2C_LS2X in Kconfig, it is not ready now
   2) Licensing issues are fixed suggested by Krzysztof Kozlowski.
   3) lsdc_pixpll_print() is removed, part of it move to debugfs.
   4) Set prefer_shadow to true if vram based driver is in using.
   5) Replace double blank lines with single line in all files
   6) Verbose cmd line parameter is replaced with drm_dbg()
   7) All warnnings reported by ./scripts/checkpatch.pl --strict are fixed
   8) Get edid from dtb support is removed as suggested by Maxime Ripard
   9) Fix typos and various improvement

v8:
   1) Drop damage update implement and its command line.
   2) Drop DRM_LSDC_VRAM_DRIVER config option as suggested by Maxime.
   3) Deduce DC's identification from its compatible property.
   4) Drop the board specific dts patch.
   5) Add documention about the display controller device node.

v9:
   1) Fix the warnnings reported by checkpatch script and fix typos


Below is a brief introduction of loongson's CPU, bridge chip and SoC.
LS2K1000 is a double core 1.0Ghz mips64r2 compatible SoC[1]. LS7A1000 is
a bridge chip made by Loongson corporation which act as north and/or south
bridge of loongson's desktop and server level processor. It is equivalent
to AMD RS780E+SB710 or something like that. More details can be read from
its user manual[2].

This bridge chip is typically use with LS3A3000, LS3A4000 and LS3A5000 cpu.
LS3A3000 is 4 core 1.45gHz mips64r2 compatible cpu.
LS3A4000 is 4 core 1.8gHz mips64r5 compatible cpu[3].
LS3A5000 is 4 core 2.5gHz loongarch cpu[4].

Nearly all loongson cpu has the hardware maintain the cache coherency,
except for early version of ls2k1000 or ls3a2000. This is the most distinct
feature from other Mips cpu.

[1] https://wiki.debian.org/InstallingDebianOn/Lemote/Loongson2K1000
[2] https://loongson.github.io/LoongArch-Documentation/Loongson-7A1000-usermanual-EN.html
[3] https://ee-paper.com/loongson-3a4000-3b4000-motherboard-products-are-compatible-with-uos-system/
[4] https://loongson.github.io/LoongArch-Documentation/Loongson-3A5000-usermanual-EN.html
[5] https://github.com/loongson-community/pmon

suijingfeng (4):
  drm/lsdc: add drm driver for loongson display controller
  MIPS: Loongson64: dts: update the display controller device node
  Documentation/dt: Add descriptions for loongson display controller
  MAINTAINERS: add maintainers for DRM LSDC driver

 .../loongson/loongson,display-controller.yaml | 114 +++
 MAINTAINERS                                   |   9 +
 .../boot/dts/loongson/loongson64-2k1000.dtsi  |   8 +
 arch/mips/boot/dts/loongson/ls7a-pch.dtsi     |   7 +-
 drivers/gpu/drm/Kconfig                       |   2 +
 drivers/gpu/drm/Makefile                      |   1 +
 drivers/gpu/drm/lsdc/Kconfig                  |  21 +
 drivers/gpu/drm/lsdc/Makefile                 |  13 +
 drivers/gpu/drm/lsdc/lsdc_connector.c         | 334 +++++++++
 drivers/gpu/drm/lsdc/lsdc_connector.h         |  38 +
 drivers/gpu/drm/lsdc/lsdc_crtc.c              | 341 +++++++++
 drivers/gpu/drm/lsdc/lsdc_drv.c               | 699 ++++++++++++++++++
 drivers/gpu/drm/lsdc/lsdc_drv.h               | 209 ++++++
 drivers/gpu/drm/lsdc/lsdc_encoder.c           |  54 ++
 drivers/gpu/drm/lsdc/lsdc_i2c.c               | 198 +++++
 drivers/gpu/drm/lsdc/lsdc_i2c.h               |  40 +
 drivers/gpu/drm/lsdc/lsdc_irq.c               |  60 ++
 drivers/gpu/drm/lsdc/lsdc_irq.h               |  20 +
 drivers/gpu/drm/lsdc/lsdc_plane.c             | 526 +++++++++++++
 drivers/gpu/drm/lsdc/lsdc_pll.c               | 580 +++++++++++++++
 drivers/gpu/drm/lsdc/lsdc_pll.h               |  90 +++
 drivers/gpu/drm/lsdc/lsdc_regs.h              | 202 +++++
 22 files changed, 3561 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/display/loongson/loongson,display-controller.yaml
 create mode 100644 drivers/gpu/drm/lsdc/Kconfig
 create mode 100644 drivers/gpu/drm/lsdc/Makefile
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_connector.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_connector.h
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_crtc.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_drv.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_drv.h
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_encoder.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_i2c.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_i2c.h
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_irq.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_irq.h
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_plane.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_pll.c
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_pll.h
 create mode 100644 drivers/gpu/drm/lsdc/lsdc_regs.h

-- 
2.25.1