xref: /kernel/linux/linux-5.10/Documentation/devicetree/bindings/c6x/dscr.txt

Device State Configuration Registers
------------------------------------

TI C6X SoCs contain a region of miscellaneous registers which provide various
function for SoC control or status. Details vary considerably among from SoC
to SoC with no two being alike.

In general, the Device State Configuration Registers (DSCR) will provide one or
more configuration registers often protected by a lock register where one or
more key values must be written to a lock register in order to unlock the
configuration register for writes. These configuration register may be used to
enable (and disable in some cases) SoC pin drivers, select peripheral clock
sources (internal or pin), etc. In some cases, a configuration register is
write once or the individual bits are write once. In addition to device config,
the DSCR block may provide registers which are used to reset peripherals,
provide device ID information, provide ethernet MAC addresses, as well as other
miscellaneous functions.

For device state control (enable/disable), each device control is assigned an
id which is used by individual device drivers to control the state as needed.

Required properties:

- compatible: must be "ti,c64x+dscr"
- reg: register area base and size

Optional properties:

  NOTE: These are optional in that not all SoCs will have all properties. For
        SoCs which do support a given property, leaving the property out of the
        device tree will result in reduced functionality or possibly driver
        failure.

- ti,dscr-devstat
    offset of the devstat register

- ti,dscr-silicon-rev
    offset, start bit, and bitsize of silicon revision field

- ti,dscr-rmii-resets
    offset and bitmask of RMII reset field. May have multiple tuples if more
    than one ethernet port is available.

- ti,dscr-locked-regs
    possibly multiple tuples describing registers which are write protected by
    a lock register. Each tuple consists of the register offset, lock register
    offsset, and the key value used to unlock the register.

- ti,dscr-kick-regs
    offset and key values of two "kick" registers used to write protect other
    registers in DSCR. On SoCs using kick registers, the first key must be
    written to the first kick register and the second key must be written to
    the second register before other registers in the area are write-enabled.

- ti,dscr-mac-fuse-regs
    MAC addresses are contained in two registers. Each element of a MAC address
    is contained in a single byte. This property has two tuples. Each tuple has
    a register offset and four cells representing bytes in the register from
    most significant to least. The value of these four cells is the MAC byte
    index (1-6) of the byte within the register. A value of 0 means the byte
    is unused in the MAC address.

- ti,dscr-devstate-ctl-regs
    This property describes the bitfields used to control the state of devices.
    Each tuple describes a range of identical bitfields used to control one or
    more devices (one bitfield per device). The layout of each tuple is:

        start_id num_ids reg enable disable start_bit nbits

    Where:
        start_id is device id for the first device control in the range
        num_ids is the number of device controls in the range
        reg is the offset of the register holding the control bits
        enable is the value to enable a device
        disable is the value to disable a device (0xffffffff if cannot disable)
        start_bit is the bit number of the first bit in the range
        nbits is the number of bits per device control

- ti,dscr-devstate-stat-regs
    This property describes the bitfields used to provide device state status
    for device states controlled by the DSCR. Each tuple describes a range of
    identical bitfields used to provide status for one or more devices (one
    bitfield per device). The layout of each tuple is:

        start_id num_ids reg enable disable start_bit nbits

    Where:
        start_id is device id for the first device status in the range
        num_ids is the number of devices covered by the range
        reg is the offset of the register holding the status bits
        enable is the value indicating device is enabled
        disable is the value indicating device is disabled
        start_bit is the bit number of the first bit in the range
        nbits is the number of bits per device status

- ti,dscr-privperm
    Offset and default value for register used to set access privilege for
    some SoC devices.


Example:

	device-state-config-regs@2a80000 {
		compatible = "ti,c64x+dscr";
		reg = <0x02a80000 0x41000>;

		ti,dscr-devstat = <0>;
		ti,dscr-silicon-rev = <8 28 0xf>;
		ti,dscr-rmii-resets = <0x40020 0x00040000>;

		ti,dscr-locked-regs = <0x40008 0x40004 0x0f0a0b00>;
		ti,dscr-devstate-ctl-regs =
			 <0 12 0x40008 1 0  0  2
			  12 1 0x40008 3 0 30  2
			  13 2 0x4002c 1 0xffffffff 0 1>;
		ti,dscr-devstate-stat-regs =
			<0 10 0x40014 1 0  0  3
			 10 2 0x40018 1 0  0  3>;

		ti,dscr-mac-fuse-regs = <0x700 1 2 3 4
					 0x704 5 6 0 0>;

		ti,dscr-privperm = <0x41c 0xaaaaaaaa>;

		ti,dscr-kick-regs = <0x38 0x83E70B13
				     0x3c 0x95A4F1E0>;
	};