&iomuxc {
/*
* Mux all pins which are unused to be GPIOs
* so they are ready for export to user space
*/
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_weim_gpio_3 &pinctrl_weim_gpio_4
&pinctrl_weim_gpio_5 &pinctrl_weim_gpio_6
&pinctrl_usbh_oc_1 &pinctrl_usbc_id_1>;
gpio {
pinctrl_pcap_1: pcap-1 {
fsl,pins = <
MX6QDL_PAD_GPIO_9__GPIO1_IO09 PAD_CTRL_HYS_PD /* SODIMM 28 */
MX6QDL_PAD_SD4_DAT2__GPIO2_IO10 PAD_CTRL_HYS_PD /* SODIMM 30 */
>;
};
};
};
With an unchanged 2.7b3 image the commands you mention to control a GPIO work fine here both in U-Boot and in Linux. If I jumper a LED to the extension connecter pin b-10 that LED reflects whatever I command.
I also guess that it works fine on your desk.
For a GPIO configured to be output the currently commanded value can not be read back unless the SION bit is set in the pad control register. Search the community for ‘SION’.
I have a 2.7b3 image where I just changed the defconfig and dts file, as mentionned above.
I just tried with kernel mainline but due to many errors, I went back to Toradex’s custom branch.
As you can see, GPIO19 is not part of the gpio{} group in my device tree file. That’s maybe the issue I’m encountering.
Also, in the documentation, there is this warning:
Warning: For i.MX 6 based modules you need to make sure that the pin is actually muxed as a GPIO in the device-tree or platform data. Failing to do so will not give any error. The pin will simply report 0 if configured as an input and not react to any state change if configured as an output.
And in the Device Tree Customization guide, it is not clear which pins can be used as GPIO directly from the user space. Do I have to put the pin in &iomuxc { pinctrl-0 = XXX } or in &iomuxc { gpio { XXX } }.
Also, what does pcap refers to ?
I’m currently using my scope to see the pin state, since the SION bit problem is well marked in the documentation.
In order to get a pin muxed one needs the pin with its configuration in dtb node which by convention has a reference name pinctrl_xxx AND then one has to add the reference to node’s pinctrl-0 property of the functionality/driver which needs these pins.
The iomuxc driver also works on its pinctrl-0 property and this can be used for pins which are not used by a particular driver, i.e. for pins which are to be used by the sysfs gpio interface.
In our device tree we group the pinctrl_xxx nodes by using function specifc nodes, e.g. the gpio node you mention. These nodes do not influence the functionality.
So GPIO_IO05 is part of the weim_gpio-3 node with reference pinctrl_weim_gpio_3 and configured to be GPIO with a pull up (and SION not set).
MX6QDL_PAD_GPIO_19__GPIO4_IO05 PAD_CTRL_HYS_PU
And that reference is added to to iomuxc’s pinctrl-0 property.
Thus the pin is muxed to be GPIO.
PCAP stands for a capacitive touch. The node you reference is likely unused in your device tree.
I’m using the Col iMX6S V1.0A on an old Col Eval V2.1c.
In this old evaluation board, some hardware buffers are soldered but there is no reason they make the thing not working.
I’ve triple checked that I’m correctly probing b-10 output in the expansion connector.
Thanks,
Léo
Edit: With SION bit configured, I have a correct returned value in the kernel, but still the same issue in u-boot and no physical change on the pin.
Edit2: GPIO works fine on GPIO2_IO10 (42) if I add the gpio group to iocmux as Max explained above. My problem seems to be related to the weim gpio banks
