Linux/AM5728: GPIO cannot be exported

Eeshan Londhe

Part Number: AM5728
Other Parts Discussed in Thread: TPS51200

Tool/software: Linux

Hi,

I am trying to enable gpio7_11 as an input on my am5728. From what I thought, the formula to convert to the pin number is gpioM_N = 32 * (M - 1) + N. This results in 32(7-1) + 11 = 203.

When I try to export the pin:

> echo 203 > /sys/class/gpio/export

I get an error saying: -sh: echo: write error: Device or resource busy

I am not sure what I may be missing as I have enabled other GPIO pins using the same way.

Let me know what I may be doing wrong! Thanks.

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

You should check whether this pin isn't used by another driver in your system.

0 Eeshan Londhe over 7 years ago in reply to Biser Gatchev-XID

Prodigy 80 points

Would you happen to know where I could find out what pins are being used already?

> cat /sys/kernel/debug/pinctrl/4a003400.pinmux/pinmux-pins shows the following:

pin 203 (PIN203): (MUX UNCLAIMED) (GPIO UNCLAIMED)

Thanks. Let me know.

0 Pavel Botev over 7 years ago in reply to Eeshan Londhe

TI__Guru**** 170625 points

Hi Eeshan,

Do you use AM57x PSDK v4.01?

Does your AM572x custom board based on AM572x EVM or IDK?

Note that this pin A22 (spi1_cs1.gpio7_11) is used for both EVM and IDK. EVM use it as DDR_VREF_OFFn signal, IDK use it as AM57XX_INDETHER_LED3_RED. To be able to export this pin from user space, you should first remove its usage from u-boot/kernel space.

Regards,
Pavel

0 Pavel Botev over 7 years ago in reply to Pavel Botev

TI__Guru**** 170625 points

Check the below files and DTS entries:

u-boot/arch/arm/dts/am57xx-beagle-x15-common.dtsi

vtt_fixed: fixedregulator-vtt {
/* TPS51200 */
..........
gpio = <&gpio7 11 GPIO_ACTIVE_HIGH>;
};

linux-kernel/arch/arm/boot/dts/am57xx-beagle-x15-common.dtsi

vtt_fixed: fixedregulator-vtt {
/* TPS51200 *
..........
gpio = <&gpio7 11 GPIO_ACTIVE_HIGH>;
};

Regards,
Pavel

0 Pavel Botev over 7 years ago in reply to Eeshan Londhe

TI__Guru**** 170625 points

Hi Eeshan,

Please close/verify this thread if you are able to resolve.

Regards,
Pavel

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Linux/AM5728: GPIO cannot be exported