(I also posted to the Beaglebone Group; please advise which group is more
appropriate)
Hello,
I'm trying to create a .dts file for a design based on the BBB, but using
the am3352b-zce60 pinout. I'm confused about how to reference several of
the devices in the Device Tree, and what "ti,hwmods" is used for.
I'm using the following files for reference (from linux-stable, and from
Dr. Molloy's "Exploring Beaglebone" book/chp06/deviceTree/DTSource3.8.13):
- am33xx.dtsi
- am335x-bone-common.dtsi
- am335x-boneblack.dts
1. Why the off-by-1 enumeration between the node name and the ti,hwmods
property for some of the devices? Examples:
i2c2: i2c@4819c000 { /* i2c2 node name,
but ti,hwmods = "i2c3"
compatible = "ti,omap4-i2c";
#address-cells = <1>;
#size-cells = <0>;
ti,hwmods = "i2c3"; /* TODO: Fix
hwmod */
reg = <0x4819c000 0x1000>;
interrupts = <30>;
status = "disabled";
};
In Dr. Molloy's version (3.8.13), this has been resolved for some devices;
in linux-stable (am33xx.dtsi), it hasn't:
uart1: serial@44e09000 { /* uart1 node name matches
ti,hwmods */
compatible = "ti,omap3-uart";
ti,hwmods = "uart1";
<<<<<<<<<<<<<<<<<<<<<<<<
clock-frequency = <48000000>;
reg = <0x44e09000 0x2000>;
interrupts = <72>;
status = "disabled";
};
In linux-stable, here's the corresponding entry in am33xx.dtsi:
uart1: serial@48022000 { /* uart1 node name, but
ti,hwmods = "uart2 */
compatible = "ti,omap3-uart";
ti,hwmods = "uart2"; <<<<<<<<<<<<<<<<<<<<<
clock-frequency = <48000000>;
reg = <0x48022000 0x2000>;
interrupts = <73>;
status = "disabled";
};
2. This also seems to be the case for the mmcs, where mmc0 isn't explicitly
defined, but &mmc2 maps to the emmc. Example:
- mmc0 is referenced explicitly in linux-stable (am335x-bone-common.dtsi)
for mapping the LEDs, but nowhere else.
- How is the reference to mmc0 resolved, given that mmc references in
am33xx.dtsi start at 1? (mmc1, mmc2, mmc3)
Thanks,
Jim
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