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
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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
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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 <[email protected]>
---
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 <[email protected]>
