[PATCH v3 00/14] Add DRM driver for Solomon SSD16xx e-paper display controllers

[Devarsh Thakkar <devarsht@ti.com>]

This series adds a DRM driver for the Solomon Systech SSD16xx family of
e-paper display controllers (SSD1673, SSD1680, SSD1681, SSD1683), starting
with support for the Gooddisplay GDEY042T81, a 4.2" 400×300 black-and-white
e-paper panel driven by the SSD1683 controller.

The driver is designed and architected keeping the bi-stable nature
and low-power requirements of epaper display based systems in mind
along with having adequate flexibility to support varying use-case
requirements for the e-paper display use-cases.

The driver integrates with the DRM atomic modesetting framework and
supports:

  - SPI communication in both 4-wire mode (separate D/C GPIO) and
    3-wire mode (9-bit SPI with embedded D/C# bit)
  - Full 4-way rotation via the Data Entry Mode register, with no GPU
    or memory-copy overhead
  - Three independently selectable refresh waveforms: partial (~300–500 ms),
    full (~1.5–2 s), and fast (~1.0–1.5 s)
  - 3-colour BWR pixel classification for panels with a red RAM plane
  - Pixel format support: XRGB8888 (color path) and R1 (native 1bpp,
    zero-copy path)
  - Runtime PM with configurable autosuspend: the controller enters
    Mode 1 deep sleep (RAM retained) after an idle timeout, waking
    transparently on the next frame update
  - System suspend/resume: switches to Mode 2 deep sleep (maximum
    power savings) on system suspend and rebuilds the pipeline on resume
  - Runtime-configurable DRM plane properties for refresh mode, colour
    mode, and session control (clear-on-init/close/disable, init-refresh
    waveform); rotation is set at probe time from a device tree property,
    and border waveform uses a fixed per-panel default

Changes from v2 [6]:

Bindings:
  - Rename the binding file to solomon,ssd1683.yaml to match an actual
    compatible, and shape the compatible as oneOf so the SSD1677 patch
    only adds a branch
  - Reference panel-common.yaml and use the common 'rotation' property
    instead of a local one that said "clockwise"
  - Add spi-3wire and document that omitting dc-gpios selects 3-wire mode

Driver core (base patch):
  - Keep lazy hardware initialization: ssd16xx_hw_init() is deferred to
    crtc_atomic_enable(); probe() performs only a GPIO reset. Follows
    the precedent of repaper.c and ssd130x.c
  - Add drm_dev_enter()/drm_dev_exit() to plane_atomic_update
  - Wrap the framebuffer read in drm_gem_fb_begin/end_cpu_access()
  - Skip the update when drm_atomic_helper_damage_merged() reports no
    damage instead of making up a full-screen rectangle
  - Remove ssd16xx_crtc_atomic_flush() and last_fb; the orientation is
    static so flush did a full hardware re-init and a second redraw on
    every commit, and last_fb had no remaining users
  - Use drm_crtc_cleanup() directly as the CRTC .destroy callback
  - Call drm_atomic_helper_check_crtc_primary_plane() from CRTC
    atomic_check
  - Send SPI data from a DMA-safe buffer in struct ssd16xx_device
    instead of the stack
  - Read XRGB8888 pixels with le32_to_cpup()
  - Size the transfer buffers per row, as the packing code does
  - Make Kconfig depend on MMU
  - GDEY042T81: use the HIZ border waveform for updates and do not
    refresh the border on every update, to avoid border flicker

Session management (clear_on_init/close/disable):
  - Split display_cleared_on_deinit into cleared_on_disable and
    cleared_on_close. A single flag made a clear on disable suppress
    the clear on close and was never re-armed on re-enable
  - Reset the RAM window before clearing and size the clear buffer per
    row
  - In 3-colour mode clear the red RAM to 0x00 (no red) instead of
    writing the all-white buffer to it, which would paint the panel red

Power management:
  - Check for damage before taking the runtime PM reference, so the
    panel is not woken up when there is nothing to draw
  - Put the panel to sleep in remove() with pm_runtime_force_suspend(),
    independent of clear_on_disable
  - Return the error from pm_runtime_force_suspend() in system suspend
  - Do not clear ->initialized again in system resume; force_resume()
    already re-initializes the hardware
  - Do not fail runtime suspend if the deep sleep command fails, as
    that would block all later resumes

Plane properties:
  - Reject 3-color mode together with partial refresh in the plane
    atomic_check, as partial refresh does not update the red channel
  - Only create the color_mode property on panels with a red plane
    instead of exposing a property with a single possible value
  - Add a mutex serializing the session state and panel access between
    atomic commits and master_set()/master_drop(); master_drop() can
    run concurrently with a nonblocking commit (e.g. on DROP_MASTER)
    and both drive the SPI bus with the same transfer buffers
  - Sync the session properties from the new plane state in
    atomic_enable as well, since it runs before plane_atomic_update
    and used the values of the previous commit

MAINTAINERS / platform integration:
  - Follow the rename of the binding file to solomon,ssd1683.yaml
  - Add the GDEY042T81 EVM overlay to the MAINTAINERS file list
  - Drop PixPaper reference from the MAINTAINERS commit message (not
    in v3)
  - DTS overlay: fix the BUSY pin name in the comments (pad 0x00b8 is
    GPMC0_CLK, not GPMC0_AD0), use GPIO_ACTIVE_HIGH for the fet-sel
    gpio-hog, fix SPDX separator to uppercase OR per SPDX-2.1, mark
    [DO_NOT_MERGE] (for driver review context only)

Changes from v1[0]:
  - Restructured into 14 modular patches covering bindings, driver core,
    features, and platform integration (was 6 patches in v1)
  - Added comprehensive device-tree bindings support for vendor prefixes
    and SSD16xx controller configurations
  - Refactored driver architecture from drm/tiny panel driver to drm/solomon
    bridge driver
  - Switch to using GEM_SHMEM helpers
  - Refactored data entry mode implementation
  - Removed runtime-configurable rotation/border-waveform DRM properties and
    their module params; rotation is now set via device tree, and border
    waveform now uses an enhanced fixed per-panel default
  - Added support for Solomon SSD1677 controller variant
  - Improved session management with plane properties
  - Added comprehensive power management support
  - Support for panels with reversed RAM X order
  - Dropped RGB888, RGB565, R8, NV12, NV16, YUYV, and UYVY format support;
    driver now only exposes XRGB8888 and R1

[0]: [V1 patch series]
https://lore.kernel.org/all/20260430183311.2978142-1-devarsht@ti.com/

[1]: [Development Branch]
https://github.com/devarsht/linux-next/tree/epaper_v3_final_4

[2]: [Test Suite]
https://github.com/devarsht/linux-next/tree/epaper_v3_final_4/tests_27sept_new8

[3]: [Test Logs]
https://github.com/devarsht/linux-next/tree/epaper_v3_final_4/tests_27sept_new8/logs

[4]: [Test Results]
https://github.com/devarsht/linux-next/tree/epaper_v3_final_4/tests_27sept_new8/results

[5]: [Result Summary]
https://github.com/devarsht/linux-next/blob/epaper_v3_final_4/tests_27sept_new8/results/run_all*.summary

[6]: [V2 Patch]
https://lore.kernel.org/all/20260927182329.4193961-1-devarsht@ti.com/

Devarsh Thakkar (13):
  dt-bindings: vendor-prefixes: Add Dalian Good Display Co., Ltd.
  dt-bindings: display: Add Solomon SSD16xx e-paper controller
  dt-bindings: display: solomon,ssd16xx: Add Solomon SSD1677 controller
  drm/solomon: Add DRM driver for Solomon SSD16xx e-paper display
    controllers
  drm/solomon: ssd16xx: Add clear_on_init/close/disable session
    management
  drm/solomon: ssd16xx: Add support for Solomon SSD1677 controller
  drm/solomon: ssd16xx: Add power management support
  drm/solomon: ssd16xx: Expose refresh mode as plane property
  drm/solomon: ssd16xx: Expose color mode as plane property
  drm/solomon: ssd16xx: Expose session management as plane properties
  MAINTAINERS: Add entry for Solomon SSD16xx DRM driver
  arm64: defconfig: Enable DRM_SSD16XX for AM62L3 EVM
  arm64: dts: ti: [DO_NOT_MERGE] Add AM62L3 EVM overlay for GDEY042T81
    e-paper display

LiangCheng Wang (1):
  drm/solomon: ssd16xx: support panels whose RAM X order is reversed

 .../bindings/display/solomon,ssd1683.yaml     |   86 +
 .../devicetree/bindings/vendor-prefixes.yaml  |    2 +
 MAINTAINERS                                   |    9 +
 arch/arm64/boot/dts/ti/Makefile               |    6 +
 .../ti/k3-am62l3-evm-epaper-gdey042t81.dtso   |   96 +
 arch/arm64/configs/defconfig                  |    1 +
 drivers/gpu/drm/solomon/Kconfig               |   13 +
 drivers/gpu/drm/solomon/Makefile              |    1 +
 drivers/gpu/drm/solomon/ssd16xx.c             | 2659 +++++++++++++++++
 9 files changed, 2873 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/solomon,ssd1683.yaml
 create mode 100644 arch/arm64/boot/dts/ti/k3-am62l3-evm-epaper-gdey042t81.dtso
 create mode 100644 drivers/gpu/drm/solomon/ssd16xx.c

-- 
2.39.1