i2c: add i2c bus driver for NVIDIA GPU

Latest NVIDIA GPU card has USB Type-C interface. There is a
Type-C controller which can be accessed over I2C.

This driver adds I2C bus driver to communicate with Type-C controller.
I2C client driver will be part of USB Type-C UCSI driver.

Signed-off-by: Ajay Gupta <ajayg@nvidia.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[wsa: kept Makefile sorting]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/i2c/busses/i2c-nvidia-gpu

@@ -0,0 +1,18 @@
+Kernel driver i2c-nvidia-gpu
+
+Datasheet: not publicly available.
+
+Authors:
+	Ajay Gupta <ajayg@nvidia.com>
+
+Description
+-----------
+
+i2c-nvidia-gpu is a driver for I2C controller included in NVIDIA Turing
+and later GPUs and it is used to communicate with Type-C controller on GPUs.
+
+If your 'lspci -v' listing shows something like the following,
+
+01:00.3 Serial bus controller [0c80]: NVIDIA Corporation Device 1ad9 (rev a1)
+
+then this driver should support the I2C controller of your GPU.

MAINTAINERS

@@ -6861,6 +6861,13 @@ L:	linux-acpi@vger.kernel.org
 S:	Maintained
 F:	drivers/i2c/i2c-core-acpi.c
 
+I2C CONTROLLER DRIVER FOR NVIDIA GPU
+M:	Ajay Gupta <ajayg@nvidia.com>
+L:	linux-i2c@vger.kernel.org
+S:	Maintained
+F:	Documentation/i2c/busses/i2c-nvidia-gpu
+F:	drivers/i2c/busses/i2c-nvidia-gpu.c
+
 I2C MUXES
 M:	Peter Rosin <peda@axentia.se>
 L:	linux-i2c@vger.kernel.org

drivers/i2c/busses/Kconfig

@@ -224,6 +224,15 @@ config I2C_NFORCE2_S4985
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-nforce2-s4985.
 
+config I2C_NVIDIA_GPU
+	tristate "NVIDIA GPU I2C controller"
+	depends on PCI
+	help
+	  If you say yes to this option, support will be included for the
+	  NVIDIA GPU I2C controller which is used to communicate with the GPU's
+	  Type-C controller. This driver can also be built as a module called
+	  i2c-nvidia-gpu.
+
 config I2C_SIS5595
 	tristate "SiS 5595"
 	depends on PCI

drivers/i2c/busses/Makefile

@@ -19,6 +19,7 @@ obj-$(CONFIG_I2C_ISCH)		+= i2c-isch.o
 obj-$(CONFIG_I2C_ISMT)		+= i2c-ismt.o
 obj-$(CONFIG_I2C_NFORCE2)	+= i2c-nforce2.o
 obj-$(CONFIG_I2C_NFORCE2_S4985)	+= i2c-nforce2-s4985.o
+obj-$(CONFIG_I2C_NVIDIA_GPU)	+= i2c-nvidia-gpu.o
 obj-$(CONFIG_I2C_PIIX4)		+= i2c-piix4.o
 obj-$(CONFIG_I2C_SIS5595)	+= i2c-sis5595.o
 obj-$(CONFIG_I2C_SIS630)	+= i2c-sis630.o