[PATCH RFC 00/10] arm64: qcom: sm6125-ginkgo: display, backlight, and touch support

["YİĞİTCAN KAVAKLI via B4 Relay" <devnull+kavakliyigitcan.gmail.com@kernel.org>]

This RFC series introduces full display, backlight, and touchscreen support
for the Xiaomi Redmi Note 8 ("ginkgo"), based on the Qualcomm SM6125 platform.

Hardware architecture summary:
1. Kinetic KTD3136 3-channel 11-bit I2C LED backlight driver.
2. Novatek NT36672A TDDI controller driving a 1080x2340 FHD+ video-mode DSI panel.
3. Novatek NT36672A SPI touchscreen interface (co-packaged within the TDDI
   controller, sharing physical reset and power lines with the display panel).
4. Qualcomm DPU 5.4 / DSI display subsystem on SM6125.

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RFC / Open Review Questions
-------------------------------------------------------------------------------

1. Panel Compatible Naming:
   - The compatible used in this series is `tianma,fhd-video-ginkgo`.
   - THIS IS AN OPEN REVIEW QUESTION. An authoritative Tianma module part
     number (e.g. TMxxxx) is not currently known or visible on accessible
     hardware markings for this OEM display module.
   - This compatible is NOT claimed as established upstream naming. We welcome
     maintainer guidance on whether to retain `tianma,fhd-video-ginkgo`, standardize
     on a board-specific or controller-specific fallback, or use an alternate convention.

2. External Touchscreen Firmware:
   - The Novatek NT36672A touchscreen controller requires SRAM firmware download.
   - Firmware is dynamically requested via request_firmware() using the name
     "novatek/nt36672a_tianma.bin" (118,784 bytes).
   - This firmware is externally loaded from userspace filesystem and NOT
     included in the kernel patches.

3. SM6125 DPU Programmable Fetch Delay:
   - On the tested SM6125 hardware, video mode output empirically requires the
     programmable fetch start counter to be offset by one horizontal total line
     (fetch_start += horiz_total).
   - Without this offset, the hardware suffers immediate DSI FIFO/TIMEOUT status=5
     errors and fails to display pixels.
   - Patch 7 models this via a catalog quirk `has_prg_fetch_delay` for SM6125.
     Reviewer feedback on whether this should be catalog-driven or handled in the
     encoder layer is appreciated.

4. MSM DSI Host Link vs Video Streaming Separation:
   - Patch 9 separates host link enable (atomic_pre_enable) from video stream
     enable (atomic_enable) to allow video-mode panels to accept DCS initialization
     packets before active pixel transmission begins.
   - Patch 8 enforces mutual exclusion between command and video modes.

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Physical Hardware Validation Summary
-------------------------------------------------------------------------------

Validation on physical Xiaomi Redmi Note 8 (SM6125) hardware:
- Display / DRM: Console text and graphical output verified crisp and stable.
- Backlight: Kinetic KTD3136 11-bit brightness scaling (0..2047) verified.
- Touchscreen: Continuous 10-second user interaction confirmed smooth 60 Hz event
  flow (985 hardware interrupts, 5034 EV_ABS events, 536 SYN_REPORT frames,
  median interval 8.36 ms).
- Lifecycle / Stress:
  * 10 / 10 consecutive isolated display OFF -> ON cycles PASSED with active
    touch verified responsive after wake on every cycle.
  * Rapid power-button spam stress PASSED without wedging display or power daemon.
  * Zero DSI FIFO errors, zero firmware load timeouts (-110, -5).

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Series Structure
-------------------------------------------------------------------------------

Patch 01: dt-bindings: backlight: add Kinetic KTD3136
Patch 02: backlight: add Kinetic KTD3136 driver
Patch 03: dt-bindings: display: panel: novatek,nt36672a: add Tianma FHD+ video mode variant
Patch 04: drm/panel: novatek-nt36672a: add Tianma FHD+ video mode panel
Patch 05: dt-bindings: input: touchscreen: add Novatek NT36672A SPI touchscreen
Patch 06: Input: novatek-nt36672a-spi: add driver for Novatek NT36672A SPI touchscreen
Patch 07: drm/msm/dpu: describe SM6125 programmable-fetch delayed-start quirk
Patch 08: drm/msm/dsi: make command and video mode configuration mutually exclusive
Patch 09: drm/msm/dsi: separate host link enable from video stream enable
Patch 10: arm64: dts: qcom: sm6125-xiaomi-ginkgo: enable display, backlight and touchscreen

Signed-off-by: YİĞİTCAN KAVAKLI <kavakliyigitcan@gmail.com>
---
YİĞİTCAN KAVAKLI (10):
      dt-bindings: backlight: add Kinetic KTD3136
      backlight: add Kinetic KTD3136 driver
      dt-bindings: display: panel: novatek,nt36672a: add Tianma FHD+ video mode variant
      drm/panel: novatek-nt36672a: add Tianma FHD+ video mode panel
      dt-bindings: input: touchscreen: add Novatek NT36672A SPI touchscreen
      Input: novatek-nt36672a-spi: add driver for Novatek NT36672A SPI touchscreen
      drm/msm/dpu: describe SM6125 programmable-fetch delayed-start quirk
      drm/msm/dsi: make command and video mode configuration mutually exclusive
      drm/msm/dsi: separate host link enable from video stream enable
      arm64: dts: qcom: sm6125-xiaomi-ginkgo: enable display, backlight and touchscreen

 .../bindings/display/panel/novatek,nt36672a.yaml   |   1 +
 .../input/touchscreen/novatek,nt36672a-spi.yaml    |  66 ++
 .../bindings/leds/backlight/kinetic,ktd3136.yaml   |  65 ++
 .../boot/dts/qcom/sm6125-xiaomi-ginkgo-common.dtsi | 100 +++
 .../gpu/drm/msm/disp/dpu1/catalog/dpu_5_4_sm6125.h |   1 +
 .../gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c   |  11 +
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h     |   2 +
 drivers/gpu/drm/msm/dsi/dsi.h                      |   1 +
 drivers/gpu/drm/msm/dsi/dsi_host.c                 |  29 +-
 drivers/gpu/drm/msm/dsi/dsi_manager.c              |  20 +
 drivers/gpu/drm/panel/panel-novatek-nt36672a.c     | 141 ++++-
 drivers/input/touchscreen/Kconfig                  |  11 +
 drivers/input/touchscreen/Makefile                 |   1 +
 drivers/input/touchscreen/novatek-nt36672a-spi.c   | 674 +++++++++++++++++++++
 drivers/video/backlight/Kconfig                    |  12 +
 drivers/video/backlight/Makefile                   |   1 +
 drivers/video/backlight/ktd3136-backlight.c        | 262 ++++++++
 17 files changed, 1362 insertions(+), 36 deletions(-)
---
base-commit: 893e11787f78e43b534e252249ac3fff4d1333f8
change-id: 20260911-ginkgo-submission-final-6703b8350357

Best regards,
-- 
YİĞİTCAN KAVAKLI <kavakliyigitcan@gmail.com>