Linux/AM3352: GPIO setting via sysfs

Hi Avner,

Do you use AM335x TI PSDK v4.03 (link below) ?

Avner Flesch said:

echo high > /sys/class/gpio/gpio117/direction

Can you try with "in" or "out", not "high". Check below pointers for more info:

linux-kernel/Documentation/gpio/sysfs.txt

Regards, Pavel

Thanks

I checked with "out" - "high" put the direction to "out" and the value to 1

I am using kernel 4.9 that I compiled by myself - because I don't want to use modules

But, I am not sure if it was compiled with the last SDK toolchain or the version before the last

Does it have any effect?

Any essential "Config"s in defconfig for that?

Thanks

Avner

Avner,

Please refer to the below pointers:

software-dl.ti.com/.../Foundational_Components.html
software-dl.ti.com/.../Foundational_Components.html

Regards,
Pavel

Thanks, Pavel,

I built the kernel with the latest SDK.

Anyway - I have also GPIO on gpio2 - that is working!

I am using busybox devmem - when I am trying to read the GPIO2/GPIO3 registers I get "Bus Error"

Another thing I have to mention is - the sysfs show that everything is correct the direction and value show the right values under ../gpio/gpio117/

As far as know - the pinmux is gpio, but I tried to read the pinmux register

Any other options?

Thanks!

Avner

Avner,

Can you provide console log output when you read GPIO3 registers and conf_mcasp0_ahclkx register with devmem2?

Make sure GPIO3 module is enabled in PRCM before trying to read its registers.

CM_PER_GPIO3_CLKCTRL

Regards,
Pavel

Pavel,

Thanks for the reply - I will do it
In case GPIO3 is disabled - the kernel do it (since it is working in the U-Boot) - I guess it is something in the DTS file, can you point me to the region that may disable it there?

Thanks

Avner

Avner,

GPIO3 is described in below DTS file (for beaglebone balck):

am33xx.dtsi, am335x-bone-common.dtsi and am335x-boneblack.dts

You stated that GPIO2 works fine, while GPIO3 not. But I can not see any difference between GPIO2 and GPIO3 in these DTS files. I think both should be enabled by default. Also I do not see any difference between GPIO2 and GPIO3 in below files, which are also related to enable GPIO2/3 modules:

linux-4.9.69/arch/arm/mach-omap2/omap_hwmod_33xx_43xx_ipblock_data.c
linux-4.9.69/arch/arm/mach-omap2/omap_hwmod_33xx_43xx_interconnect_data.c

You can try to add below entry in your main DTS file (i.e. am335x-boneblack.dts) and check if there will be any difference:

&gpio3 {
status = "okay";
};

Check for reference the below DTS file:

am43x-gp-evm.dts

Regards,
Pavel

Pavel,

Here are the dumps (I am using omapconf tool):

read register conf_mcasp0_ahclkx/0x44E109AC:

~ # omapconf read 0x44e109ac
00000030

CM_PER_GPIO3_CLKCTRL:

| CM_PER_GPIO3_CLKCTRL       | 0x44E000B4   | 0x00030000 |

GPIO3 registers:

~ # omapconf read 0x4481ae000
Segmentation fault

Thanks

Avner

OK - got it the module is disabled
Where can I change this? in the dts?

Avner Flesch said:

read register conf_mcasp0_ahclkx/0x44E109AC:

~ # omapconf read 0x44e109ac
00000030

Seems that your gpio3_21 pin is not pinmuxed properly. In this register, you should have: 0x17

[2:0] mode  = 0x7 (gpio3_21)

[5] rx_active = 0 (output pin)

For how to make proper pinmux, refer to the am335x-bonebalck.dts file for reference.

AM33XX_IOPAD(0x9ac, PIN_OUTPUT_PULLDOWN | MUX_MODE7) /* mcasp0_ahclkx.GPIO3_21*/

Avner Flesch said:

CM_PER_GPIO3_CLKCTRL:

| CM_PER_GPIO3_CLKCTRL       | 0x44E000B4   | 0x00030000 |

GPIO3 registers:

~ # omapconf read 0x4481ae000
Segmentation fault

GPIO3 registers start address is 0x481AE000  (not 0x4481AE000)

Regards,
Pavel

Avner Flesch said:

OK - got it the module is disabled
Where can I change this? in the dts?

You can try to add below entry in your main DTS file (i.e. am335x-boneblack.dts) and check if there will be any difference:

&gpio3 {
status = "okay";
};