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…t/torvalds/linux-2.6 Conflicts: drivers/ata/libata-scsi.c include/linux/libata.h Futher merge of Linus's head and compilation fixups. Signed-Off-By: David Howells <[email protected]>
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MPC52xx Device Tree Bindings | ||
---------------------------- | ||
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(c) 2006 Secret Lab Technologies Ltd | ||
Grant Likely <grant.likely at secretlab.ca> | ||
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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 Firmare (IEEE 1275) compatible firmware using an OF compatible | ||
client interface API. | ||
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This document specifies the requirements on the device-tree for mpc52xx | ||
based boards. These requirements are above and beyond the details | ||
specified in either the OpenFirmware spec or booting-without-of.txt | ||
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All new mpc52xx-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. | ||
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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 52xx board. If all 52xx boards | ||
follow the same convention, then generic 52xx support code will work | ||
rather than coding special cases for each new board. | ||
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This section tries to capture the thought process behind why the naming | ||
convention is what it is. | ||
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1. Node 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, MPC52xx boards must have an 'soc5200' node as a child of the | ||
root node. | ||
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The soc5200 node holds child nodes for all on chip devices. 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'. | ||
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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. | ||
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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 mpc52xx, the required format for each compatible value is | ||
<chip>-<device>[-<mode>]. At the minimum, the list shall contain two | ||
items; the first specifying the exact chip, and the second specifying | ||
mpc52xx for the chip. | ||
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ie. ethernet on mpc5200b: compatible = "mpc5200b-ethernet\0mpc52xx-ethernet" | ||
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The idea here is that most drivers will match to the most generic field | ||
in the compatible list (mpc52xx-*), but can also test the more specific | ||
field for enabling bug fixes or extra features. | ||
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Modal devices, like PSCs, also append the configured function to the | ||
end of the compatible field. ie. A PSC in i2s mode would specify | ||
"mpc52xx-psc-i2s", not "mpc52xx-i2s". This convention is chosen to | ||
avoid naming conflicts with non-psc devices providing the same | ||
function. For example, "mpc52xx-spi" and "mpc52xx-psc-spi" describe | ||
the mpc5200 simple spi device and a PSC spi mode respectively. | ||
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If the soc device is more generic and present on other SOCs, the | ||
compatible property can specify the more generic device type also. | ||
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ie. mscan: compatible = "mpc5200-mscan\0mpc52xx-mscan\0fsl,mscan"; | ||
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At the time of writing, exact chip may be either 'mpc5200' or | ||
'mpc5200b'. | ||
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Device drivers should always try to match as generically as possible. | ||
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III - Structure | ||
=============== | ||
The device tree for an mpc52xx board follows the structure defined in | ||
booting-without-of.txt with the following additional notes: | ||
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0) the root node | ||
---------------- | ||
Typical root description node; see booting-without-of | ||
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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 | ||
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2) The memory node | ||
------------------ | ||
Typical memory description node; see booting-without-of. | ||
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3) The soc5200 node | ||
------------------- | ||
This node describes the on chip SOC peripherals. Every mpc52xx based | ||
board will have this node, and as such there is a common naming | ||
convention for SOC devices. | ||
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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> | ||
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Recommended properties: | ||
name type description | ||
---- ---- ----------- | ||
compatible string should be "<chip>-soc\0mpc52xx-soc" | ||
ie. "mpc5200b-soc\0mpc52xx-soc" | ||
#interrupt-cells int must be <3>. If it is not defined | ||
here then it must be defined in every | ||
soc device node. | ||
bus-frequency int IPB bus frequency in HZ. Clock rate | ||
used by most of the soc devices. | ||
Defining it here avoids needing it | ||
added to every device node. | ||
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4) soc5200 child nodes | ||
---------------------- | ||
Any on chip SOC devices available to Linux must appear as soc5200 child nodes. | ||
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Note: in the tables below, '*' matches all <chip> values. ie. | ||
*-pic would translate to "mpc5200-pic\0mpc52xx-pic" | ||
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Required soc5200 child nodes: | ||
name device_type compatible Description | ||
---- ----------- ---------- ----------- | ||
cdm@<addr> cdm *-cmd Clock Distribution | ||
pic@<addr> interrupt-controller *-pic need an interrupt | ||
controller to boot | ||
bestcomm@<addr> dma-controller *-bestcomm 52xx pic also requires | ||
the bestcomm device | ||
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Recommended soc5200 child nodes; populate as needed for your board | ||
name device_type compatible Description | ||
---- ----------- ---------- ----------- | ||
gpt@<addr> gpt *-gpt General purpose timers | ||
rtc@<addr> rtc *-rtc Real time clock | ||
mscan@<addr> mscan *-mscan CAN bus controller | ||
pci@<addr> pci *-pci PCI bridge | ||
serial@<addr> serial *-psc-uart PSC in serial mode | ||
i2s@<addr> i2s *-psc-i2s PSC in i2s mode | ||
ac97@<addr> ac97 *-psc-ac97 PSC in ac97 mode | ||
spi@<addr> spi *-psc-spi PSC in spi mode | ||
irda@<addr> irda *-psc-irda PSC in IrDA mode | ||
spi@<addr> spi *-spi MPC52xx spi device | ||
ethernet@<addr> network *-fec MPC52xx ethernet device | ||
ata@<addr> ata *-ata IDE ATA interface | ||
i2c@<addr> i2c *-i2c I2C controller | ||
usb@<addr> usb-ohci-be *-ohci,ohci-be USB controller | ||
xlb@<addr> xlb *-xlb XLB arbritrator | ||
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IV - Extra Notes | ||
================ | ||
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1. Interrupt mapping | ||
-------------------- | ||
The mpc52xx 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. | ||
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The interrupts property for device nodes using the mpc52xx pic consists | ||
of three cells; <L1 L2 level> | ||
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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] |
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