AM5708: Interrupt not instantly detected

Johan

Part Number: AM5708

Hello,

I have a strange phenomena with our CPU board

The CPU board has a Atmel MXT touch controller connected to the I2C. We have used this in the past with the touch controller interrupt line configured as "IRQ_TYPE_EDGE_FALLING". This worked fine until a i2c error messes up the data reading from the Atmel which will then keep its interrupt low. And we never see a new falling edge. So no new touch events.

We have changed the interrupt to IRQ_TYPE_LEVEL_LOW same as the example configuration for the Atmel device. Now the handler function is not called straight after the interrupt occurs. There can be several seconds of delay here.

What I also noticed that if I trigger a different interrupt after a touch interrupt the the handler gets called instantly. For example when I press the enter key on the serial console it will instantly handle the touch interrupt.

The configuration for the device:

&i2c2 {
    status = "okay";
    clock-frequency = <100000>;
    touch: touch@4a {
        compatible = "atmel,maxtouch";
        reg = <0x4a>;
        interrupt-parent = <&gpio5>;
        interrupts = <3 IRQ_TYPE_LEVEL_LOW>;
    };
};

We are running Linux 4.4.41.

Is there some sort of explanation for this behaviour? I'm a bit stumped here.

Kind regards,

Johan

over 2 years ago

0 Josue Zamitiz-Ayala over 2 years ago

TI__Mastermind 32155 points

Hello Johan,

Please allow a day for me to investigate this. DISCLAIMER: This is legacy code, the latest SDK uses Linux kernel 5.10, so it is harder for us to support.

Is this board a TI board or custom board?

-Josue

0 Johan over 2 years ago in reply to Josue Zamitiz-Ayala

Prodigy 70 points

Hello Josue,

Have you had the chance to investigate further?

This is a custom board.

Kind regards,

Johan

0 Josue Zamitiz-Ayala over 2 years ago in reply to Johan

TI__Mastermind 32155 points

Hello Johan,

I appreciate your patience. I will look at this this week.

Josue

0 Josue Zamitiz-Ayala over 2 years ago in reply to Josue Zamitiz-Ayala

TI__Mastermind 32155 points

Hello Johan,

Could you please upload a log of the error?

-Josue

0 Johan over 1 year ago in reply to Josue Zamitiz-Ayala

Prodigy 70 points

Hello Josue

I haven't got any error logs. I only have output from a logical analyzer showing the delay between the interrupt and the data retrieval which should be triggered the ISR:

Zoomed in at ca. 40s:

I haven't been able to use the latest kernel, but I have been able to try with a "newer" 4.19.73 kernel which gives the same results.

Kind regards,

Johan

0 Josue Zamitiz-Ayala over 1 year ago in reply to Johan

TI__Mastermind 32155 points

Hello Johan,

Could you expand on:

Johan said:
We have used this in the past with the touch controller interrupt line configured as "IRQ_TYPE_EDGE_FALLING". This worked fine until a i2c error messes up the data reading from the Atmel which will then keep its interrupt low.

At what point was this working "fine", and what changed?

Johan said:
a i2c error messes up the data reading from the Atmel which will then keep its interrupt low.

This error is essentially what you see above right?

In terms of the DTS entry I see both IRQ_TYPE_LEVEL_LOW and IRQ_TYPE_EDGE_FALLING being used, as well as this example from an am335 DTS:

&i2c1 {
        pinctrl-names = "default";
        pinctrl-0 = <&i2c1_pins>;
        clock-frequency = <100000>;
        status = "okay";

        atmel: atmel_mxt_ts@4a {
                compatible = "atmel,maxtouch";
                reg = <0x4a>;
                interrupt-parent = <&gpio1>;
                interrupts = <28 8>;
                gpios = <&gpio3 18 GPIO_ACTIVE_HIGH>;
        };

source

-Josue

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AM5708: Interrupt not instantly detected