On Fri, Jan 16, 2015 at 2:57 PM, Jim Giles <gdwo...@gmail.com> wrote:
> (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)
btw, don't use 3.8.x as the "set" in stone naming.. A few things such
as the gpio where mis-numbered and later corrected in mainline.
That aside.. In kernel land, most devices start with xyz0 where as
"marketing" people call this xyz1, i guess it's hard to sell something
to a customer labeled as xyz0..
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am33xx.dtsi
Regards,
--
Robert Nelson
http://www.rcn-ee.com/
--
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