Pinmuxing with devicetree (beaglebone)

Pinmuxing with devicetree (beaglebone)

[Tim Sander]

Hi

I am currently trying to get pinmuxing working on a beaglebone board with an 
offtree driver. This is for a custom handbuild hardware so i guess there is no 
point in bringing this mainline.

While this is havyly patched 3.8.4 version running over here i think the
pinmux infrastructure is the new standard way. At least there is a 
pinctrl/44e10800.pinmux directory in debugfs?

My last aproach was using the devicetree but beeing new to this devicetree 
stuff i just got stuck: 
http://comments.gmane.org/gmane.linux.ports.arm.kernel/231204

Now i tried use the way it is described in Documentation/pinctrl.txt but still 
there are the includes missing: #include <linux/pinctrl/consumer.h>.

Also while there is a /sys/kernel/debug/pinctrl/44e10800.pinmux in debugfs i 
found that not so intuitive as the omap_mux which disappeared. Also i didn't 
find any documentation for this debugfs stuff.

So what is the recommended way to get this stupid pinmuxing going. In pre 
devicetree days one would just pick the mux.h include of the platform and 
initialized the muxers which was pretty straight forward. Now with device tree 
its much more complicated. No proper syntax checking as with the c definitions 
and no documentation how to get this magic stuff working :-(.

The whole stuff is build by a ptxdist (a embedded buildsystem) and can be 
found over here:
https://gitorious.org/ptxdist-beaglebone/ptxdist-beaglebone

Best regards
Tim

Re: Pinmuxing with devicetree (beaglebone)

[Haojian Zhuang]

On Sun, Apr 21, 2013 at 5:43 PM, Tim Sander <tim@krieglstein.org> wrote:
> Hi
>
> I am currently trying to get pinmuxing working on a beaglebone board with an
> offtree driver. This is for a custom handbuild hardware so i guess there is no
> point in bringing this mainline.
>
> While this is havyly patched 3.8.4 version running over here i think the
> pinmux infrastructure is the new standard way. At least there is a
> pinctrl/44e10800.pinmux directory in debugfs?
>
> My last aproach was using the devicetree but beeing new to this devicetree
> stuff i just got stuck:
> http://comments.gmane.org/gmane.linux.ports.arm.kernel/231204
>
> Now i tried use the way it is described in Documentation/pinctrl.txt but still
> there are the includes missing: #include <linux/pinctrl/consumer.h>.
>
> Also while there is a /sys/kernel/debug/pinctrl/44e10800.pinmux in debugfs i
> found that not so intuitive as the omap_mux which disappeared. Also i didn't
> find any documentation for this debugfs stuff.
>
> So what is the recommended way to get this stupid pinmuxing going. In pre
> devicetree days one would just pick the mux.h include of the platform and
> initialized the muxers which was pretty straight forward. Now with device tree
> its much more complicated. No proper syntax checking as with the c definitions
> and no documentation how to get this magic stuff working :-(.
>
> The whole stuff is build by a ptxdist (a embedded buildsystem) and can be
> found over here:
> https://gitorious.org/ptxdist-beaglebone/ptxdist-beaglebone
>
"pins" node could dump the register configuration if it's pinctrl-single driver.

You can dump this to check whether the right pinmux is set.

I checked your patch in the link.  It seems that you only write the pinmux
configuration without using them.

Don't forget to append this in your DTS file.
     pinctrl-names = "default";
       pinctrl-0 = <&wind_pins>;

There're two documents worth to read for enabling pins for
pinctrl-single driver.
Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt
Documentation/devicetree/bindings/pinctrl/pinctrl-single.txt

Regards
Haojian

> Best regards
> Tim
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: Pinmuxing with devicetree (beaglebone)

[Tim Sander]

Hi Haojian and Linux-Folks

Thanks for your reply. This is just a short followup how i got it working. But
as the 3.8.4 kernel on the beaglebone is having no ethernet connectivity i 
went back to the 3.2 kernel without device tree support for the time beeing.
So i didn't spent to much time on the device tree stuff.
> > I am currently trying to get pinmuxing working on a beaglebone board with
> > an offtree driver. This is for a custom handbuild hardware so i guess
> > there is no point in bringing this mainline.
> > 
> > While this is havyly patched 3.8.4 version running over here i think the
> > pinmux infrastructure is the new standard way. At least there is a
> > pinctrl/44e10800.pinmux directory in debugfs?
> > 
> > My last aproach was using the devicetree but beeing new to this
> > devicetree stuff i just got stuck:
> > http://comments.gmane.org/gmane.linux.ports.arm.kernel/231204
> > 
> > Now i tried use the way it is described in Documentation/pinctrl.txt but
> > still there are the includes missing: #include
> > <linux/pinctrl/consumer.h>.
> > 
> > Also while there is a /sys/kernel/debug/pinctrl/44e10800.pinmux in
> > debugfs i found that not so intuitive as the omap_mux which disappeared.
> > Also i didn't find any documentation for this debugfs stuff.
> > 
> > So what is the recommended way to get this stupid pinmuxing going. In pre
> > devicetree days one would just pick the mux.h include of the platform and
> > initialized the muxers which was pretty straight forward. Now with device
> > tree its much more complicated. No proper syntax checking as with the c
> > definitions and no documentation how to get this magic stuff working
> > :-(.
> > 
> > The whole stuff is build by a ptxdist (a embedded buildsystem) and can be
> > found over here:
> > https://gitorious.org/ptxdist-beaglebone/ptxdist-beaglebone
> 
> "pins" node could dump the register configuration if it's pinctrl-single
> driver.
> 
> You can dump this to check whether the right pinmux is set.
> 
> I checked your patch in the link.  It seems that you only write the pinmux
> configuration without using them.
> 
> Don't forget to append this in your DTS file.
>      pinctrl-names = "default";
>        pinctrl-0 = <&wind_pins>;
Thanks for the pointers, but somehow these fragments didn't work. What worked 
was writing it directly into the included dtb at the proper place eg.:

   am33xx_pinmux: pinmux@44e10800 {
      pinctrl-names = "default";
      pinctrl-0 = <&userleds_pins>;

      userled_pins: pinmux_userled_pins {
         pinctrl-single,pins = <
            /* Tims wind pins */
            0x000  0x27      /* gpmc_ad0 = ad0 = P8-25 = gpio1_0|input, no pullup, gpio mux  */
            0x004  0x27      /* gpmc_ad1 = ad1 = P8-24 = gpio1_1|input, no pullup, gpio mux  */
            0x008  0x27      /* gpmc_ad2 = ad2 = P8-5 = gpio1_2|input, no pullup, gpio mux  */
            0x00c  0x27      /* gpmc_ad3 = ad3 = P8-6 = gpio1_3|input, no pullup, gpio mux  */
            0x038  0x26      /* gpmc_ad14  = pru_gpio_in14 = P8_16 = gpio1.14|input, no pullup, pru0 gpio 14 */

            0x54 0x7 /* gpmc_a5.gpio1_21, OUTPUT | MODE7 */
            0x58 0x17   /* gpmc_a6.gpio1_22, OUTPUT_PULLUP | MODE7 */
            0x5c 0x7 /* gpmc_a7.gpio1_23, OUTPUT | MODE7 */
            0x60 0x17   /* gpmc_a8.gpio1_24, OUTPUT_PULLUP | MODE7 */
         >;
      };
      i2c0_pins: pinmux_i2c0_pins {
         pinctrl-single,pins = <
            0x188 0x70  /* i2c0_sda, SLEWCTRL_SLOW | INPUT_PULLUP | MODE0 */
            0x18c 0x70  /* i2c0_scl, SLEWCTRL_SLOW | INPUT_PULLUP | MODE0 */
         >;
      };
      i2c2_pins: pinmux_i2c2_pins {
         pinctrl-single,pins = <
            0x178 0x73  /* uart1_ctsn.i2c2_sda, SLEWCTRL_SLOW | INPUT_PULLUP | MODE3 */
            0x17c 0x73  /* uart1_rtsn.i2c2_scl, SLEWCTRL_SLOW | INPUT_PULLUP | MODE3 */
         >;
      };
   };

Also one thing i didn't know is that the dtb can also reverse compile so that the result can be seen.
This is especially handy with these fragment and include stuff.

Best regards
Tim