Linux/AM4378: GPIO pin number

Arockia winiston

Expert 2035 points

Part Number: AM4378
Other Parts Discussed in Thread: AM4372

Tool/software: Linux

Dear,

Our board is broadly based on AM437X-gp-evm and SDK is 4.02. I am using General purpose pin for my isolated input and output.

I am using some of the pins from GPIO0, GPIO1, GPIO2, GPIO4 and GPIO5

I tried with GPIO0_24 as given below from calculation (0x32+24 = 24).

root@x-gp-evm:/sys/class/gpio# echo 24 > export

root@x-gp-evm:/sys/class/gpio/gpio24# echo "out" > direction

root@x-gp-evm:/sys/class/gpio/gpio24# echo 1 > value

It works good.

But GPIO5_4 in the user space, i have calculated like (5x32)+4= 164 and entered as given below in my console.

root@x-gp-evm:/sys/class/gpio# echo 164 > export

But it says below error

" [ 44.513931] export_store: invalid GPIO 164

-sh echo: write error: Invalid argument".

If i execute, "root@x-gp-evm:/sys/class/gpio# ls ", i got below message.

export gpio16 gpiogpio0 gpiochip32 gpiochip64 unexport.

GPIO5 related dts entries as given below

&gpio5 {
pinctrl-names = "default";
pinctrl-0 = <&gpio5_pins_default>;
status = "okay";

p28 {
gpio-hog;
gpios = <28 GPIO_ACTIVE_LOW>;
output-high;
lines-name = "rs232-2-TX-Enable";
};
p29 {
gpio-hog;
gpios = <29 GPIO_ACTIVE_LOW>;
output-high;
lines-name = "rs232-1-TX-Enable";
};
};

gpio5_pins_default: gpio5_pins_default {
pinctrl-single,pins = <
0x250 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (P25) spi4_sclk.gpio5[4] */
0x254 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (R24) spi4_d0.gpio5[5] */
0x258 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (P24) spi4_d1.gpio5[6] */
0x25c ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (N25) spi4_cs0.gpio5[7] */
0x238 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (D25) gpio5_8.gpio5[8] */
0x23c ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (F24) gpio5_9.gpio5[9] */
0x244 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (F23) gpio5_11.gpio5[11] */
/*extra 3 digital input entry for adding 8 gpi */
0x24c ( PIN_INPUT_PULLUP | MUX_MODE7 ) /* (E24) gpio5_13.gpio5[13] */
0x208 ( PIN_INPUT_PULLUP | MUX_MODE7 ) /* (AE18) cam0_data0.gpio5[19] */
0x20c ( PIN_INPUT_PULLUP | MUX_MODE7 ) /* (AB18) cam0_data1.gpio5[20] */
/* 4 output pin for rs485 direction control */
0x270 ( PIN_OUTPUT_PULLUP | MUX_MODE9 ) /* (D24) xdma_event_intr0.gpio5[28] */
0x274 ( PIN_OUTPUT_PULLUP | MUX_MODE9 ) /* (C24) xdma_event_intr1.gpio5[29] */
0x230 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (H22) uart3_ctsn.gpio5[0] */
0x234 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (K24) uart3_rtsn.gpio5[1] */
>;
};

How do i calculate GPIO pin(GPIO0 to GPIO5) and set in the user space?

Regards,

Winiston.P

over 7 years ago

0 Pavel Botev over 7 years ago

TI__Guru**** 170625 points

Hi Winiston,

You are trying to export gpio5_4 (164) pin in sysfs, but you have not described that pin in DTS file.

Can you try to export gpio5_28 (188) and gpio5_29 (189) in sysfs, do you have the same result?

Regards,
Pavel

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

Expert 2035 points

Dear Pavel,

First line is for gpio5_4(164) in my dts file. Entry for gpio5_4 as given below in my dts file.

0x250 ( PIN_OUTPUT_PULLUP | MUX_MODE7 ) /* (P25) spi4_sclk.gpio5[4] */

I tried gpio5_28(188) and gpio5_29(189). But i got the same result.

I tried gpio4_24 (152). It works fine. Is there any mistake in my GPIO5 declaration in my dts file ?

Regards,

Winiston.P

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

TI__Guru**** 170625 points

Winiston,

I have tried to export GPIO5 pin on AM437x TI EVM and observe the same issue as you. Seems like we have different scheme for GPIO5 pins.

For example, on AM437x TI EVM, gpio5_8 pin is used to select between LCD and HDMI display, we have this description in DTS file:
linux-kernel/arch/arm/boot/dts/am437x-gp-evm.dts

&gpio5 {
pinctrl-names = "default";
pinctrl-0 = <&display_mux_pins>;
status = "okay";
ti,no-reset-on-init;

p8 {
/*
* SelLCDorHDMI selects between display and audio paths:
* Low: HDMI display with audio via HDMI
* High: LCD display with analog audio via aic3111 codec
*/
gpio-hog;
gpios = <8 GPIO_ACTIVE_HIGH>;
output-high;
line-name = "SelLCDorHDMI";
};
};

display_mux_pins: display_mux_pins {
pinctrl-single,pins = <
/* GPIO 5_8 to select LCD / HDMI */
AM4372_IOPAD(0xa38, PIN_OUTPUT_PULLUP | MUX_MODE7)
>;
};

Then, in user space we have:

root@am437x-evm:/sys/class/gpio# ls
export gpio16 gpiochip0 gpiochip128 gpiochip32 gpiochip510 gpiochip64 gpiochip96 unexport
root@am437x-evm:/sys/class/gpio# cat /sys/kernel/debug/gpio
gpiochip4: GPIOs 128-159, parent: platform/48322000.gpio, gpio:
gpio-136 ( |SelLCDorHDMI ) out hi

The kernel map GPIO5 to gpiochip4, and pin gpio5_8 to gpio-136.

Check how this apply to your custom board. See also below e2e thread:

e2e.ti.com/.../1794050

Regards,
Pavel

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

TI__Guru**** 170625 points

Winiston,

If you have no more questions related to the subject, please close/verify/resolve this thread.

Regards,
Pavel

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

Expert 2035 points

Dear Pavel,

GPIO pin number works as you said. It solved my problem. As you said, GPIO5 to gpiochip4. So gpio5_8 to gpio-136. Similarly GPIO4 to gpiochip3, GPIO3 to gpiochip2.

Then how does GPIO0 always remain gpiochip0?

Regards,

Winiston.P

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

TI__Guru**** 170625 points

Winiston,

Check below pointers for more info how gpio pin is calculated:

e2e.ti.com/.../701154
www.emcraft.com/.../controlling-gpio-from-linux-user-space

Regards,
Pavel

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

Intellectual 625 points

Thanks Pavel !! this helps

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Linux/AM4378: GPIO pin number