linux-kernel - Re: Pinmuxing with devicetree (beaglebone)

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Date:	Thu, 2 May 2013 00:24:46 +0200
From:	Tim Sander <tim@...eglstein.org>
To:	Haojian Zhuang <haojian.zhuang@...il.com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Pinmuxing with devicetree (beaglebone)

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@...10800 {
      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
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