| Message ID | 1425284686-5116-3-git-send-email-wens@csie.org |
|---|---|
| State | Superseded, archived |
| Headers | show |
On Mon, Mar 02, 2015 at 04:24:44PM +0800, Chen-Yu Tsai wrote: > Reduced Serial Bus (RSB) is an SMBus like bus used to communicate > with some PMICs (like the AXP223) or other peripherals. > > The RSB DT bindings are pretty much the same as the one defined for > the marvell's mv64xxx controller, with the additional RSB specific > "allwinner,rsb-hw-addr" property for slave device nodes. > > There are 2 types of addresses for RSB devices, a hardware address > and a runtime (software) configurable address. The former is only > used when configuring the latter. All read/write accesses use the > runtime address. > > It would seem straightforward to use the hardware address in the > DT bindings as the slave's address. However this will not work as > the hardware address is 12 bits wide, and at least 1 device, the > AC100 audio codec, has the highest bit set. This address would be > incompatible with I2C (7 or 10 bit addresses) and likely rejected. > > Hence this binding uses statically allocated (by the author of the > DT) runtime addresses for the slave's "reg" property. The hardware > address is put in a separete named property. When writing a new DT, ^ separate > the author must take care to not have multiple slave devices use > the same address. It is recommended to follow whatever conventions > the hardware vendor uses. While very complete, the three last paragraphs should rather be, or at least duplicated, in the file itself. Maxime
diff --git a/Documentation/devicetree/bindings/i2c/i2c-sunxi-rsb.txt b/Documentation/devicetree/bindings/i2c/i2c-sunxi-rsb.txt new file mode 100644 index 000000000000..9b1f2dd2e17a --- /dev/null +++ b/Documentation/devicetree/bindings/i2c/i2c-sunxi-rsb.txt @@ -0,0 +1,54 @@ + +* Allwinner RSB (Reduced Serial Bus) controller + +Required properties : + + - reg : Offset and length of the register set for the device. + - compatible : Should be "allwinner,sun8i-a23-rsb". + - interrupts : The interrupt line connected to the RSB peripheral. + - clocks : The gate clk connected to the RSB peripheral. + - resets : The reset line connected to the RSB peripheral. + - #address-cells : always 1 (for RSB runtime addresses) + - #size-cells : always 0 + +Optional properties : + + - clock-frequency : Desired RSB bus clock frequency in Hz. If not set + the default frequency is 100kHz. Maximum is 20MHz. + +An RSB device node may contain up to 15 child nodes each encoding an RSB +slave device. + +Slave device properties: + Required properties: + - reg : The runtime address used to access the device. + - allwinner,rsb-hw-addr : The RSB hardware address for the device. This + is only used when configuring the runtime + address of the device. + + Valid runtime addresses - There are only 15 valid runtime addresses: + + 0x17, 0x2d, 0x3a, 0x4e, 0x59, 0x63, 0x74, 0x8b, + 0x9c, 0xa6, 0xb1, 0xc5, 0xd2, 0xe8, 0xff + + +Example: + + rsb@01f03400 { + compatible = "allwinner,sun8i-a23-rsb"; + reg = <0x01f03400 0x400>; + interrupts = <0 39 4>; + clocks = <&apb0_gates 3>; + clock-frequency = <3000000>; + resets = <&apb0_rst 3>; + #address-cells = <1>; + #size-cells = <0>; + + axp223: pmic@2d { + compatible = "x-powers,axp223", "x-powers,axp221"; + reg = <0x2d>; + allwinner,rsb-hw-addr = <0x3e3>; + + /* ... */ + }; + };
Reduced Serial Bus (RSB) is an SMBus like bus used to communicate with some PMICs (like the AXP223) or other peripherals. The RSB DT bindings are pretty much the same as the one defined for the marvell's mv64xxx controller, with the additional RSB specific "allwinner,rsb-hw-addr" property for slave device nodes. There are 2 types of addresses for RSB devices, a hardware address and a runtime (software) configurable address. The former is only used when configuring the latter. All read/write accesses use the runtime address. It would seem straightforward to use the hardware address in the DT bindings as the slave's address. However this will not work as the hardware address is 12 bits wide, and at least 1 device, the AC100 audio codec, has the highest bit set. This address would be incompatible with I2C (7 or 10 bit addresses) and likely rejected. Hence this binding uses statically allocated (by the author of the DT) runtime addresses for the slave's "reg" property. The hardware address is put in a separete named property. When writing a new DT, the author must take care to not have multiple slave devices use the same address. It is recommended to follow whatever conventions the hardware vendor uses. Signed-off-by: Chen-Yu Tsai <wens@csie.org> --- .../devicetree/bindings/i2c/i2c-sunxi-rsb.txt | 54 ++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/devicetree/bindings/i2c/i2c-sunxi-rsb.txt