>
> I ran into this last week when configuring an I2C RTC device, and I have
> not seen this mentioned in the group.
Angstrom for the BBB, at least the most recent version, has a selection of
device tree files, both in source and precompiled form. I used them as a
basis for my own Beagleboard NTPD device tree. I've found an ambiguous
address reference that tripped me up.
Consider this segment of a device tree for an I2C RTC device, such as the
Dallas DS1307, or the DS3231 (packaged as the Chronodot, which I have).
I've omitted most of it for clarity:
> fragment@1 {
> target = <&i2c2>;
>
> __overlay__ {
> /* shut up DTC warnings */
> #address-cells = <1>;
> #size-cells = <0>;
>
> /* DS1307 RTC module */
> rtc@68 {
> compatible = "dallas,ds1307";
> reg = <0x68>;
> };
> };
> }
>
Note the rtc@68 address. This is ambiguous. The real address of this
device is 0x68 in hex. The DTC parser must interpret numeric values in a
default decimal radix, unless it has a hex digit already in it; another
device I have is addressed as 3C, which is represented correctly.
My RTC was not being detected by the kernel. The fix is simple: always
insert the 0x prefix for all addresses (represented in most databooks in
hex); the corrected reference is rtc@0x68. My Chronodot was since
detected by the kernel with no fuss.
I've "decompiled" the original binary device tree file
(BB-BONE-RTC-00A0.dtbo) and it matches the source (BB-BONE-RTC-00A0.dts) as
far as the address reference is concerned.
I believe this would affect all I2C devices represented in the device
tree. I haven't had the chance to scan the other device tree files. I am
running this on a Beaglebone White, but I have both species of Beaglebone
(white and black) and they both are running the latest Angstrom so this
problem appears to still exist.
I've attached a corrected version of the BB-BONE-RTC-00A0.dts file.
Regards,
Dave M.
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/*
* Copyright (C) 2013 Matt Ranostay <[email protected]>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
/dts-v1/;
/plugin/;
/*
* Pin assignments
*
* Module Connector
* SCL -> P9.19
* SDA <- P9.20
* SQW/PPS <- P9.15
*
*/
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black";
part-number = "BB-BONE-RTC-01";
version = "00A0";
/* state the resources this cape uses */
exclusive-use =
/* the pin header uses */
"P9.15"; /*gpio1_16 */
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
pps_pins: pinmux_pps_pins {
pinctrl-single,pins = <
0x040 0x27 /* gpmc_a0.gpio1_16,
INPUT | PULLDIS | MODE7 */
>;
};
};
};
fragment@1 {
target = <&i2c2>;
__overlay__ {
/* shut up DTC warnings */
#address-cells = <1>;
#size-cells = <0>;
/* DS1307 RTC module */
rtc@0x68 {
compatible = "dallas,ds1307";
reg = <0x68>;
};
};
};
fragment@2 {
target = <&ocp>;
__overlay__ {
pps {
compatible = "pps-gpio";
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&pps_pins>;
gpios = <&gpio2 16 0>;
assert-falling-edge;
};
};
};
};
