PRU and dts for IO definition in kernel 3.1x ?

[Cedric Malitte]

Hi,

so trying to get my things up and running, I wrote a program for the PRU in asm to toggle 2 pins and read 4.

In C, I manage to manipulate them because I'm using GPIO.

But in asm... I try to interact with r30 and r31, and nothing really happens...

I"m with kernel 3.15.

Could someone guide me ? 

I think I have to add a dts to declare pins and pinmux, but I feel a bit lost on this point.

In case, this is my asm source

#include "pru.h"

#include "pru_macros.hp"

.origin 0

.entrypoint MAIN

MAIN:

 /* enable ocp wide accesses */

 LBCO r0, CONST_PRUCFG, 4, 4

 CLR r0, r0, 4

 SBCO r0, CONST_PRUCFG, 4, 4

 /* prepared pru to host shared memory */

 MOV r0, 0x000000120

 MOV r1, CTPPR_0

 ST32 r0, r1

 MOV r0, 0x00100000

 MOV r1, CTPPR_1

 ST32 r0, r1

 MOV r10, 0

 MOV r11, 0

 MOV r12, 0

 /* main */

LOOP1:

SET r30.t15  /* CLK high */

MOV r10, r31.b0 /* Read in the data */

QBBC CHKSENSOR2, r10.b0.t0 /* if r10.0, set r11.0 */

SET r11, 0  

CHKSENSOR2:

QBBC CHKSENSOR3, r10.b0.t1 /* if r10.1, set r11.15 */

SET r11, 15

CHKSENSOR3:

QBBC CHKSENSOR4, r10.b0.t2 /* if r10.2, set r12.0 */

SET r12, 0

CHKSENSOR4:

QBBC ENDCHECK, r10.b0.t3 /* if r10.3, set r12.15 */

SET r12, 15

ENDCHECK:

CLR r30.t15 /* CLK low  */     

LSL r11, r11, 1

LSL r12, r12, 1

ADD r0, r0, 1

JMP LOOP1

 /* store results from r10,r11 into host memory */

 SBCO r10, CONST_PRUSHAREDRAM, 0, 8

 /* signal cpu we are done (never reached) */

 MOV r31.b0, PRU0_ARM_INTERRUPT + 16

 HALT

Thanks,

Cedric

[Cedric Malitte]

Ok finally managed to build a dts using compatible='gpio-leds' for outputs and I now have a 15Mhz output.

I'll investigate why when I try to use pru code compiled from C, the signal has a weird shape on the scope but using asm, it's a regular one.

For inputs, I do not know yet if I should use compatible="gpio-keys" or something else, I did not find anything related to this yet.

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[Jon E]

Hi,

I have some simple examples of direct reading/writing under 3.8 (setting mode 6, exclusive use etc)..

https://github.com/dresco/pru_examples

Have the device tree definitions have changed for 3.1x? I've not yet successfully built my PRU code under the new 3.14 kernel, so perhaps bone-pinmux-helper is no longer an option?

Regards,

Jon

[Cedric Malitte]

Hi Jon,

Yes under 3.1x some things have changed a bit for dts.

I failed with bone-pinmux-helper when I tried.

It's still a WIP for me and also a LIP ( learn in progress :) )

Regards,

Cedric

[Robert Nelson]

On Thu, Sep 25, 2014 at 8:05 AM, Cedric Malitte
<cedric....@gmail.com> wrote:
> Hi Jon,
>
> Yes under 3.1x some things have changed a bit for dts.
> I failed with bone-pinmux-helper when I tried.
>
> It's still a WIP for me and also a LIP ( learn in progress :) )

The v3.14.x branch here: (1) uses pinmux-helper..

https://github.com/beagleboard/linux/tree/3.14

Regards,

--
Robert Nelson
http://www.rcn-ee.com/

[Cedric Malitte]

Thanks Robert,

will check that.

Cedric