Documentation/powerpc/mpc52xx-device-tree-bindings.txt - linux/kernel/git/mellanox/linux - Git at Google

 MPC5200 Device Tree Bindings
 ----------------------------

 (c) 2006-2007 Secret Lab Technologies Ltd
 Grant Likely <grant.likely at secretlab.ca>

 ********** DRAFT ***********
 * WARNING: Do not depend on the stability of these bindings just yet.
 * The MPC5200 device tree conventions are still in flux
 * Keep an eye on the linuxppc-dev mailing list for more details
 ********** DRAFT ***********

 I - Introduction
 ================
 Boards supported by the arch/powerpc architecture require device tree be
 passed by the boot loader to the kernel at boot time.  The device tree
 describes what devices are present on the board and how they are
 connected.  The device tree can either be passed as a binary blob (as
 described in Documentation/powerpc/booting-without-of.txt), or passed
 by Open Firmware (IEEE 1275) compatible firmware using an OF compatible
 client interface API.

 This document specifies the requirements on the device-tree for mpc5200
 based boards.  These requirements are above and beyond the details
 specified in either the Open Firmware spec or booting-without-of.txt

 All new mpc5200-based boards are expected to match this document.  In
 cases where this document is not sufficient to support a new board port,
 this document should be updated as part of adding the new board support.

 II - Philosophy
 ===============
 The core of this document is naming convention.  The whole point of
 defining this convention is to reduce or eliminate the number of
 special cases required to support a 5200 board.  If all 5200 boards
 follow the same convention, then generic 5200 support code will work
 rather than coding special cases for each new board.

 This section tries to capture the thought process behind why the naming
 convention is what it is.

 1.  names
 ---------
 There is strong convention/requirements already established for children
 of the root node.  'cpus' describes the processor cores, 'memory'
 describes memory, and 'chosen' provides boot configuration.  Other nodes
 are added to describe devices attached to the processor local bus.

 Following convention already established with other system-on-chip
 processors, 5200 device trees should use the name 'soc5200' for the
 parent node of on chip devices, and the root node should be its parent.

 Child nodes are typically named after the configured function.  ie.
 the FEC node is named 'ethernet', and a PSC in uart mode is named 'serial'.

 2. device_type property
 -----------------------
 similar to the node name convention above; the device_type reflects the
 configured function of a device.  ie. 'serial' for a uart and 'spi' for
 an spi controller.  However, while node names *should* reflect the
 configured function, device_type *must* match the configured function
 exactly.

 3. compatible property
 ----------------------
 Since device_type isn't enough to match devices to drivers, there also
 needs to be a naming convention for the compatible property.  Compatible
 is an list of device descriptions sorted from specific to generic.  For
 the mpc5200, the required format for each compatible value is
 <chip>-<device>[-<mode>].  The OS should be able to match a device driver
 to the device based solely on the compatible value.  If two drivers
 match on the compatible list; the 'most compatible' driver should be
 selected.

 The split between the MPC5200 and the MPC5200B leaves a bit of a
 conundrum.  How should the compatible property be set up to provide
 maximum compatibility information; but still accurately describe the
 chip?  For the MPC5200; the answer is easy.  Most of the SoC devices
 originally appeared on the MPC5200.  Since they didn't exist anywhere
 else; the 5200 compatible properties will contain only one item;
 "mpc5200-<device>".

 The 5200B is almost the same as the 5200, but not quite.  It fixes
 silicon bugs and it adds a small number of enhancements.  Most of the
 devices either provide exactly the same interface as on the 5200.  A few
 devices have extra functions but still have a backwards compatible mode.
 To express this information as completely as possible, 5200B device trees
 should have two items in the compatible list;
 "mpc5200b-<device>\0mpc5200-<device>".  It is *strongly* recommended
 that 5200B device trees follow this convention (instead of only listing
 the base mpc5200 item).

 If another chip appear on the market with one of the mpc5200 SoC
 devices, then the compatible list should include mpc5200-<device>.

 ie. ethernet on mpc5200: compatible = "mpc5200-ethernet"
     ethernet on mpc5200b: compatible = "mpc5200b-ethernet\0mpc5200-ethernet"

 Modal devices, like PSCs, also append the configured function to the
 end of the compatible field.  ie. A PSC in i2s mode would specify
 "mpc5200-psc-i2s", not "mpc5200-i2s".  This convention is chosen to
 avoid naming conflicts with non-psc devices providing the same
 function.  For example, "mpc5200-spi" and "mpc5200-psc-spi" describe
 the mpc5200 simple spi device and a PSC spi mode respectively.

 If the soc device is more generic and present on other SOCs, the
 compatible property can specify the more generic device type also.

 ie. mscan: compatible = "mpc5200-mscan\0fsl,mscan";

 At the time of writing, exact chip may be either 'mpc5200' or
 'mpc5200b'.

 Device drivers should always try to match as generically as possible.

 III - Structure
 ===============
 The device tree for an mpc5200 board follows the structure defined in
 booting-without-of.txt with the following additional notes:

 0) the root node
 ----------------
 Typical root description node; see booting-without-of

 1) The cpus node
 ----------------
 The cpus node follows the basic layout described in booting-without-of.
 The bus-frequency property holds the XLB bus frequency
 The clock-frequency property holds the core frequency

 2) The memory node
 ------------------
 Typical memory description node; see booting-without-of.

 3) The soc5200 node
 -------------------
 This node describes the on chip SOC peripherals.  Every mpc5200 based
 board will have this node, and as such there is a common naming
 convention for SOC devices.

 Required properties:
 name			type		description
 ----			----		-----------
 device_type		string		must be "soc"
 ranges			int		should be <0 baseaddr baseaddr+10000>
 reg			int		must be <baseaddr 10000>
 compatible		string		mpc5200: "mpc5200-soc"
 					mpc5200b: "mpc5200b-soc\0mpc5200-soc"
 system-frequency	int		Fsystem frequency; source of all
 					other clocks.
 bus-frequency		int		IPB bus frequency in HZ.  Clock rate
 					used by most of the soc devices.
 #interrupt-cells	int		must be <3>.

 Recommended properties:
 name			type		description
 ----			----		-----------
 model			string		Exact model of the chip;
 					ie: model="fsl,mpc5200"
 revision		string		Silicon revision of chip
 					ie: revision="M08A"

 The 'model' and 'revision' properties are *strongly* recommended.  Having
 them presence acts as a bit of a safety net for working around as yet
 undiscovered bugs on one version of silicon.  For example, device drivers
 can use the model and revision properties to decide if a bug fix should
 be turned on.

 4) soc5200 child nodes
 ----------------------
 Any on chip SOC devices available to Linux must appear as soc5200 child nodes.

 Note: The tables below show the value for the mpc5200.  A mpc5200b device
 tree should use the "mpc5200b-<device>\0mpc5200-<device> form.

 Required soc5200 child nodes:
 name		device_type		compatible	Description
 ----		-----------		----------	-----------
 cdm@<addr>	cdm			mpc5200-cmd	Clock Distribution
 pic@<addr>	interrupt-controller	mpc5200-pic	need an interrupt
 							controller to boot
 bestcomm@<addr>	dma-controller		mpc5200-bestcomm 5200 pic also requires
 							 the bestcomm device

 Recommended soc5200 child nodes; populate as needed for your board
 name		device_type	compatible	  Description
 ----		-----------	----------	  -----------
 gpt@<addr>	gpt		fsl,mpc5200-gpt	  General purpose timers
 rtc@<addr>	rtc		mpc5200-rtc	  Real time clock
 mscan@<addr>	mscan		mpc5200-mscan	  CAN bus controller
 pci@<addr>	pci		mpc5200-pci	  PCI bridge
 serial@<addr>	serial		mpc5200-psc-uart  PSC in serial mode
 i2s@<addr>	sound		mpc5200-psc-i2s	  PSC in i2s mode
 ac97@<addr>	sound		mpc5200-psc-ac97  PSC in ac97 mode
 spi@<addr>	spi		mpc5200-psc-spi	  PSC in spi mode
 irda@<addr>	irda		mpc5200-psc-irda  PSC in IrDA mode
 spi@<addr>	spi		mpc5200-spi	  MPC5200 spi device
 ethernet@<addr>	network		mpc5200-fec	  MPC5200 ethernet device
 ata@<addr>	ata		mpc5200-ata	  IDE ATA interface
 i2c@<addr>	i2c		mpc5200-i2c	  I2C controller
 usb@<addr>	usb-ohci-be	mpc5200-ohci,ohci-be	USB controller
 xlb@<addr>	xlb		mpc5200-xlb	  XLB arbitrator

 Important child node properties
 name		type		description
 ----		----		-----------
 cell-index	int		When multiple devices are present, is the
 				index of the device in the hardware (ie. There
 				are 6 PSC on the 5200 numbered PSC1 to PSC6)
 				    PSC1 has 'cell-index = <0>'
 				    PSC4 has 'cell-index = <3>'

 5) General Purpose Timer nodes (child of soc5200 node)
 On the mpc5200 and 5200b, GPT0 has a watchdog timer function.  If the board
 design supports the internal wdt, then the device node for GPT0 should
 include the empty property 'fsl,has-wdt'.

 6) PSC nodes (child of soc5200 node)
 PSC nodes can define the optional 'port-number' property to force assignment
 order of serial ports.  For example, PSC5 might be physically connected to
 the port labeled 'COM1' and PSC1 wired to 'COM1'.  In this case, PSC5 would
 have a "port-number = <0>" property, and PSC1 would have "port-number = <1>".

 PSC in i2s mode:  The mpc5200 and mpc5200b PSCs are not compatible when in
 i2s mode.  An 'mpc5200b-psc-i2s' node cannot include 'mpc5200-psc-i2s' in the
 compatible field.

 IV - Extra Notes
 ================

 1. Interrupt mapping
 --------------------
 The mpc5200 pic driver splits hardware IRQ numbers into two levels.  The
 split reflects the layout of the PIC hardware itself, which groups
 interrupts into one of three groups; CRIT, MAIN or PERP.  Also, the
 Bestcomm dma engine has it's own set of interrupt sources which are
 cascaded off of peripheral interrupt 0, which the driver interprets as a
 fourth group, SDMA.

 The interrupts property for device nodes using the mpc5200 pic consists
 of three cells; <L1 L2 level>

     L1 := [CRIT=0, MAIN=1, PERP=2, SDMA=3]
     L2 := interrupt number; directly mapped from the value in the
           "ICTL PerStat, MainStat, CritStat Encoded Register"
     level := [LEVEL_HIGH=0, EDGE_RISING=1, EDGE_FALLING=2, LEVEL_LOW=3]

 2. Shared registers
 -------------------
 Some SoC devices share registers between them.  ie. the i2c devices use
 a single clock control register, and almost all device are affected by
 the port_config register.  Devices which need to manipulate shared regs
 should look to the parent SoC node.  The soc node is responsible
 for arbitrating all shared register access.
	MPC5200 Device Tree Bindings
	----------------------------

	(c) 2006-2007 Secret Lab Technologies Ltd
	Grant Likely <grant.likely at secretlab.ca>

	******** DRAFT *********
	* WARNING: Do not depend on the stability of these bindings just yet.
	* The MPC5200 device tree conventions are still in flux
	* Keep an eye on the linuxppc-dev mailing list for more details
	******** DRAFT *********

	I - Introduction
	================
	Boards supported by the arch/powerpc architecture require device tree be
	passed by the boot loader to the kernel at boot time. The device tree
	describes what devices are present on the board and how they are
	connected. The device tree can either be passed as a binary blob (as
	described in Documentation/powerpc/booting-without-of.txt), or passed
	by Open Firmware (IEEE 1275) compatible firmware using an OF compatible
	client interface API.

	This document specifies the requirements on the device-tree for mpc5200
	based boards. These requirements are above and beyond the details
	specified in either the Open Firmware spec or booting-without-of.txt

	All new mpc5200-based boards are expected to match this document. In
	cases where this document is not sufficient to support a new board port,
	this document should be updated as part of adding the new board support.

	II - Philosophy
	===============
	The core of this document is naming convention. The whole point of
	defining this convention is to reduce or eliminate the number of
	special cases required to support a 5200 board. If all 5200 boards
	follow the same convention, then generic 5200 support code will work
	rather than coding special cases for each new board.

	This section tries to capture the thought process behind why the naming
	convention is what it is.

	1. names
	---------
	There is strong convention/requirements already established for children
	of the root node. 'cpus' describes the processor cores, 'memory'
	describes memory, and 'chosen' provides boot configuration. Other nodes
	are added to describe devices attached to the processor local bus.

	Following convention already established with other system-on-chip
	processors, 5200 device trees should use the name 'soc5200' for the
	parent node of on chip devices, and the root node should be its parent.

	Child nodes are typically named after the configured function. ie.
	the FEC node is named 'ethernet', and a PSC in uart mode is named 'serial'.

	2. device_type property
	-----------------------
	similar to the node name convention above; the device_type reflects the
	configured function of a device. ie. 'serial' for a uart and 'spi' for
	an spi controller. However, while node names should reflect the
	configured function, device_type must match the configured function
	exactly.

	3. compatible property
	----------------------
	Since device_type isn't enough to match devices to drivers, there also
	needs to be a naming convention for the compatible property. Compatible
	is an list of device descriptions sorted from specific to generic. For
	the mpc5200, the required format for each compatible value is
	<chip>-<device>[-<mode>]. The OS should be able to match a device driver
	to the device based solely on the compatible value. If two drivers
	match on the compatible list; the 'most compatible' driver should be
	selected.

	The split between the MPC5200 and the MPC5200B leaves a bit of a
	conundrum. How should the compatible property be set up to provide
	maximum compatibility information; but still accurately describe the
	chip? For the MPC5200; the answer is easy. Most of the SoC devices
	originally appeared on the MPC5200. Since they didn't exist anywhere
	else; the 5200 compatible properties will contain only one item;
	"mpc5200-<device>".

	The 5200B is almost the same as the 5200, but not quite. It fixes
	silicon bugs and it adds a small number of enhancements. Most of the
	devices either provide exactly the same interface as on the 5200. A few
	devices have extra functions but still have a backwards compatible mode.
	To express this information as completely as possible, 5200B device trees
	should have two items in the compatible list;
	"mpc5200b-<device>\0mpc5200-<device>". It is strongly recommended
	that 5200B device trees follow this convention (instead of only listing
	the base mpc5200 item).

	If another chip appear on the market with one of the mpc5200 SoC
	devices, then the compatible list should include mpc5200-<device>.

	ie. ethernet on mpc5200: compatible = "mpc5200-ethernet"
	ethernet on mpc5200b: compatible = "mpc5200b-ethernet\0mpc5200-ethernet"

	Modal devices, like PSCs, also append the configured function to the
	end of the compatible field. ie. A PSC in i2s mode would specify
	"mpc5200-psc-i2s", not "mpc5200-i2s". This convention is chosen to
	avoid naming conflicts with non-psc devices providing the same
	function. For example, "mpc5200-spi" and "mpc5200-psc-spi" describe
	the mpc5200 simple spi device and a PSC spi mode respectively.

	If the soc device is more generic and present on other SOCs, the
	compatible property can specify the more generic device type also.

	ie. mscan: compatible = "mpc5200-mscan\0fsl,mscan";

	At the time of writing, exact chip may be either 'mpc5200' or
	'mpc5200b'.

	Device drivers should always try to match as generically as possible.

	III - Structure
	===============
	The device tree for an mpc5200 board follows the structure defined in
	booting-without-of.txt with the following additional notes:

	0) the root node
	----------------
	Typical root description node; see booting-without-of

	1) The cpus node
	----------------
	The cpus node follows the basic layout described in booting-without-of.
	The bus-frequency property holds the XLB bus frequency
	The clock-frequency property holds the core frequency

	2) The memory node
	------------------
	Typical memory description node; see booting-without-of.

	3) The soc5200 node
	-------------------
	This node describes the on chip SOC peripherals. Every mpc5200 based
	board will have this node, and as such there is a common naming
	convention for SOC devices.

	Required properties:
	name type description
	---- ---- -----------
	device_type string must be "soc"
	ranges int should be <0 baseaddr baseaddr+10000>
	reg int must be <baseaddr 10000>
	compatible string mpc5200: "mpc5200-soc"
	mpc5200b: "mpc5200b-soc\0mpc5200-soc"
	system-frequency int Fsystem frequency; source of all
	other clocks.
	bus-frequency int IPB bus frequency in HZ. Clock rate
	used by most of the soc devices.
	#interrupt-cells int must be <3>.

	Recommended properties:
	name type description
	---- ---- -----------
	model string Exact model of the chip;
	ie: model="fsl,mpc5200"
	revision string Silicon revision of chip
	ie: revision="M08A"

	The 'model' and 'revision' properties are strongly recommended. Having
	them presence acts as a bit of a safety net for working around as yet
	undiscovered bugs on one version of silicon. For example, device drivers
	can use the model and revision properties to decide if a bug fix should
	be turned on.

	4) soc5200 child nodes
	----------------------
	Any on chip SOC devices available to Linux must appear as soc5200 child nodes.

	Note: The tables below show the value for the mpc5200. A mpc5200b device
	tree should use the "mpc5200b-<device>\0mpc5200-<device> form.

	Required soc5200 child nodes:
	name device_type compatible Description
	---- ----------- ---------- -----------
	cdm@<addr> cdm mpc5200-cmd Clock Distribution
	pic@<addr> interrupt-controller mpc5200-pic need an interrupt
	controller to boot
	bestcomm@<addr> dma-controller mpc5200-bestcomm 5200 pic also requires
	the bestcomm device

	Recommended soc5200 child nodes; populate as needed for your board
	name device_type compatible Description
	---- ----------- ---------- -----------
	gpt@<addr> gpt fsl,mpc5200-gpt General purpose timers
	rtc@<addr> rtc mpc5200-rtc Real time clock
	mscan@<addr> mscan mpc5200-mscan CAN bus controller
	pci@<addr> pci mpc5200-pci PCI bridge
	serial@<addr> serial mpc5200-psc-uart PSC in serial mode
	i2s@<addr> sound mpc5200-psc-i2s PSC in i2s mode
	ac97@<addr> sound mpc5200-psc-ac97 PSC in ac97 mode
	spi@<addr> spi mpc5200-psc-spi PSC in spi mode
	irda@<addr> irda mpc5200-psc-irda PSC in IrDA mode
	spi@<addr> spi mpc5200-spi MPC5200 spi device
	ethernet@<addr> network mpc5200-fec MPC5200 ethernet device
	ata@<addr> ata mpc5200-ata IDE ATA interface
	i2c@<addr> i2c mpc5200-i2c I2C controller
	usb@<addr> usb-ohci-be mpc5200-ohci,ohci-be USB controller
	xlb@<addr> xlb mpc5200-xlb XLB arbitrator

	Important child node properties
	name type description
	---- ---- -----------
	cell-index int When multiple devices are present, is the
	index of the device in the hardware (ie. There
	are 6 PSC on the 5200 numbered PSC1 to PSC6)
	PSC1 has 'cell-index = <0>'
	PSC4 has 'cell-index = <3>'

	5) General Purpose Timer nodes (child of soc5200 node)
	On the mpc5200 and 5200b, GPT0 has a watchdog timer function. If the board
	design supports the internal wdt, then the device node for GPT0 should
	include the empty property 'fsl,has-wdt'.

	6) PSC nodes (child of soc5200 node)
	PSC nodes can define the optional 'port-number' property to force assignment
	order of serial ports. For example, PSC5 might be physically connected to
	the port labeled 'COM1' and PSC1 wired to 'COM1'. In this case, PSC5 would
	have a "port-number = <0>" property, and PSC1 would have "port-number = <1>".

	PSC in i2s mode: The mpc5200 and mpc5200b PSCs are not compatible when in
	i2s mode. An 'mpc5200b-psc-i2s' node cannot include 'mpc5200-psc-i2s' in the
	compatible field.

	IV - Extra Notes
	================

	1. Interrupt mapping
	--------------------
	The mpc5200 pic driver splits hardware IRQ numbers into two levels. The
	split reflects the layout of the PIC hardware itself, which groups
	interrupts into one of three groups; CRIT, MAIN or PERP. Also, the
	Bestcomm dma engine has it's own set of interrupt sources which are
	cascaded off of peripheral interrupt 0, which the driver interprets as a
	fourth group, SDMA.

	The interrupts property for device nodes using the mpc5200 pic consists
	of three cells; <L1 L2 level>

	L1 := [CRIT=0, MAIN=1, PERP=2, SDMA=3]
	L2 := interrupt number; directly mapped from the value in the
	"ICTL PerStat, MainStat, CritStat Encoded Register"
	level := [LEVEL_HIGH=0, EDGE_RISING=1, EDGE_FALLING=2, LEVEL_LOW=3]

	2. Shared registers
	-------------------
	Some SoC devices share registers between them. ie. the i2c devices use
	a single clock control register, and almost all device are affected by
	the port_config register. Devices which need to manipulate shared regs
	should look to the parent SoC node. The soc node is responsible
	for arbitrating all shared register access.