NVIDIA: SAUCE: MEDIATEK: pinctrl: mediatek: Add EINT Driver for CX7 hot plug on DGX Spark

This driver is used to manage PCIe link for NVIDIA ConnectX-7 (CX7)
hot-plug/unplug on DGX Spark. We need to disable PCIe link when
CX7 cable plug out happens and enable pcie link when
CX7 cable plug in happens.
This behavior is needed to conserve power when the CX7 cable is unplugged.
Otherwise, the CX7 controllers would still consume power and negatively impact the
board’s overall power consumption.
This driver helps save power when the CX7 cable is absent.

The driver detects cable hot‑plug or unplug events, enables or disables the corresponding links,
emits udev events, and then the user space triggers removal and rescanning of the PCIe device.

It also creates a sysfs entry to emulate cable plug in/out
behavior as below:

plug in - echo 1 > /sys/devices/platform/MTKP0001:00/cx7_dbg/plugin
plug out - echo 0 > /sys/devices/platform/MTKP0001:00/cx7_dbg/plugin

We also implement uevent to notify user-space applications when a
cable is plugged in or removed. Below are the details of our process:

* cable plug-in:
    Report plug-in uevent (driver)
    Power on CX7
    Enable PCIe link (application)
    Rescan CX7 devices (application)

* cable removal:
    Report removal uevent (driver)
    Remove CX7 devices (application)
    Disable PCIe link (application)
    Power off CX7

Testing performed includes:
1. Repeated CX7 plug/unplug cycles, verifying that the PCIe link transitions correctly.
2. Ensured no side effects or hangs.
3. Hence, regression risk is considered to be low.
4. It is also being tested by SW QA.

Automated testing:
We have included the dgx-spark-mlnx-hotplug package in the BaseOS, which provides a
standalone userspace script that can be used for automated testing.
To validate the driver without manual intervention, run the following:
1. Plug-in:
    /opt/nvidia/dgx-spark-mlnx-hotplug/mtk-hotplug-handler.sh plug-in
2. Unplug:
    /opt/nvidia/dgx-spark-mlnx-hotplug/mtk-hotplug-handler.sh removal
3. After each operation, run lspci and verify the results:
    * When plugged-in: The output should show
      “Ethernet controller: Mellanox Technologies MT2910 Family [ConnectX-7]” PCIe devices.
    * When plugged-out: There should be no PCIe device entry with
      “Ethernet controller: Mellanox Technologies MT2910 Family [ConnectX-7]”.

We plan to upstream this driver during the merge window for the next Linux kernel release,
expected to open in the January-February 2026 timeframe(anticipated to be kernel 6.20).
Necessary support will be provided.

Signed-off-by: Vaibhav Vyas <vavyas@nvidia.com>
Signed-off-by: Jerry.Guo <jerry.guo@mediatek.com>
Signed-off-by: Yenchia Chen <yenchia.chen@mediatek.com>
Signed-off-by: Shubhi Garg <shgarg@nvidia.com>
Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com>
Signed-off-by: Surabhi Chythanya Kumar <schythanyaku@nvidia.com>

Author: schythanyaku

debian.nvidia-6.14/config/annotations

@@ -224,6 +224,7 @@ CONFIG_CC_HAS_SIGN_RETURN_ADDRESS               policy<{'arm64': '-'}>
 CONFIG_CC_VERSION_TEXT                          policy<{'amd64': '"x86_64-linux-gnu-gcc-13 (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0"', 'arm64': '"aarch64-linux-gnu-gcc-13 (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0"'}>
 CONFIG_CGROUP_RESCTRL                           policy<{'amd64': '-', 'arm64': '-'}>
 CONFIG_CPUFREQ_ARCH_CUR_FREQ                    policy<{'amd64': 'y'}>
+CONFIG_EINT_MTK_HP                              policy<{'arm64': 'm'}>
 CONFIG_DRM_PANIC_SCREEN_QR_CODE                 policy<{'amd64': '-', 'arm64': '-'}>
 CONFIG_EC_HUAWEI_GAOKUN                         policy<{'arm64': 'n'}>
 CONFIG_FTRACE_SORT_STARTUP_TEST                 policy<{'amd64': 'n', 'arm64': 'n'}>

drivers/pinctrl/mediatek/Kconfig

@@ -10,6 +10,15 @@ config EINT_MTK
 	default y if PINCTRL_MTK || PINCTRL_MTK_MOORE
 	default PINCTRL_MTK_PARIS
 
+config EINT_MTK_HP
+	tristate "MediaTek HP Driver"
+	depends on EINT_MTK
+	help
+	  Say yes here to support NICs cable plug in/out test.
+	  It will disable pcie link when plug out and enable
+	  pcie link after plug in cable.
+	  This is particularly useful for MediaTek MT8901 SoC.
+
 config PINCTRL_MTK
 	bool
 	depends on OF

drivers/pinctrl/mediatek/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 # Core
 obj-$(CONFIG_EINT_MTK)			+= mtk-eint.o
+obj-$(CONFIG_EINT_MTK_HP)		+= mtk-eint-hotplug.o
 obj-$(CONFIG_PINCTRL_MTK)		+= pinctrl-mtk-common.o
 obj-$(CONFIG_PINCTRL_MTK_V2)		+= pinctrl-mtk-common-v2.o
 obj-$(CONFIG_PINCTRL_MTK_MTMIPS)	+= pinctrl-mtmips.o