i2c: Add a generic i2c driver

This adds a generic I2C driver that can be described in the devicetree
and used to generate ACPI objects in the SSDT based on the information
provided in the config registers.

The I2C bus can be configured and the device can provide an interrupt and
wake capability to the OS.  A configuration option allows for a GPIO to
be provided that will be checked to determine if the device is preset on
the board before including it in the generated SSDT.

The driver is generic enough to be used for basic I2C devices that do
not have special configuration needs such as touchpads, touchscreens,
sensors, some audio codec/amplifiers, etc.

Sample usage for a touchpad device:

device pci 15.1 on
  chip drivers/i2c/generic
    register "hid" = ""ELAN0000""
    register "desc" = "ELAN Touchpad"
    register "irq" = "IRQ_EDGE_LOW(GPP_B3_IRQ)"
    register "wake" = "GPE0_DW0_05"
    device i2c 15.0 on end
  end
end

Will result in the following code in the SSDT:

Scope (\_SB.PCI0.I2C1) {
  Device (D015) {
    Name (_HID, "ELAN0000")
    Name (_UID, 0)
    Name (_S0W, 4)
    Name (_PRW, Package () { 5, 3 })
    Method (_STA) { Return (0x0f) }
    Name (_CRS, ResourceTemplate () {
      I2cSerialBus (0x15, ControllerInitiated, 400000, AddressingMode7Bit,
                    "\\_S.PCI0.I2C1", 0, ResourceConsumer)
      Interrupt (ResourceConsumer, Edge, ActiveLow) { 51 }
    })
  }
}

Change-Id: Ib32055720835b70e91ede5e4028ecd91894d70d5
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/15016
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/drivers/i2c/generic/Kconfig b/src/drivers/i2c/generic/Kconfig
new file mode 100644
index 0000000000..a4c01048aa
--- /dev/null
+++ b/src/drivers/i2c/generic/Kconfig
@@ -0,0 +1,2 @@
+config DRIVERS_I2C_GENERIC
+	bool