AM335x ADC hangs SDK8

Radu Donos

Hi All,

Recently we migrate from SDK6 (kernel 3.2.0) to SDK8 (kernel 3.14.26), and I have a problem with config ADC (no TouchScreen, only ADC) into DT.

I need to config AIN5 and AIN6 in One-shot Mode.

With old kernel it work fine with config:

static struct adc_data am335x_adc_data = { 
    .adc_channels = 8,
};
static struct mfd_tscadc_board tscadc = {
    .adc_init = &am335x_adc_data,
};
static void adc_init(void)
{
    int err;
    pr_info("Enable ADC...\n");
    err = am33xx_register_mfd_tscadc(&tscadc);
    if (err)
        pr_err("failed to register ADC/Touchscreen device\n");
}

My device tree for kernel 3.14:

#include "am33xx.dtsi"

&tscadc {
	status = "okay";
	adc {
		ti,adc-channels = <5 6 7>;
	};
};

I tried to use as in old kernel:

echo "oneshot" > /sys/bus/iio/devices/iio\:device0/mode
cat /sys/bus/iio/devices/iio\:device0/in_voltage5_raw

On first read in_voltage5_raw cat print follow error: "Resource temporarily unavailable", on second read it hangs.

I try to debug adc driver (drivers/iio/adc/ti_am335x_adc.c), and the drivet hang on call function am335x_tsc_se_set_once(adc_dev->mfd_tscadc, step_en);

Also I found the following related to this topic: https://e2e.ti.com/support/arm/sitara_arm/f/791/p/413600/1468952, but can't find solution for my problem.

into menuconfig I have enabled:

CONFIG_MFD_TI_AM335X_TSCADC=y
CONFIG_TI_AM335X_ADC=y

Can someone help me with ADC configuration (or help me to solve hang problem)?

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi Radu,

Please check this wiki: http://processors.wiki.ti.com/index.php/Linux_Core_ADC_User's_Guide

0 Radu Donos over 10 years ago in reply to Biser Gatchev-XID

Prodigy 130 points

Hi Biser,

I checked my configuration is exactly as in Your recommendation (Driver Configuration), also Device Tree looks like in Your recommendation, but it not work.

The driver hang on function am335x_tsc_se_set_once (see my question).
It may need to initialize any clk something else?

0 Radu Donos over 10 years ago in reply to Radu Donos

Prodigy 130 points

Hi all,

I found solution for may problem. We have 2 types of boards with and witout adc, and I run my tests on board without ADC (VDDA_ADC not connected), and conversion not starting.

On first read we have IDLE state into REG_ADCFSM, configure ADC, but conversion not started and adc return -EAGAIN.

On second read, adc stepts are already configured, and driver wait idle (into REG_ADCFSM) to reconfigure steps for new conversion, but.. because adc not powered (not running), we will not have idle state, and driver pending event inf cycle.

For solve this bug, I change follow lines into file drivers/mfd/ti_am335x_tscadc.c:

--- a/drivers/mfd/ti_am335x_tscadc.c    2015-05-05 09:50:49.654710300 +0300
+++ b/drivers/mfd/ti_am335x_tscadc.c       2015-05-21 11:33:26.581552200 +0300
@@ -64,6 +64,7 @@ void am335x_tsc_se_set_cache(struct ti_t
 }
 EXPORT_SYMBOL_GPL(am335x_tsc_se_set_cache);

+#define GET_ADC_TIMEOUT_US 500000 //500ms
 static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc)
 {
        DEFINE_WAIT(wait);
@@ -82,7 +83,7 @@ static void am335x_tscadc_need_adc(struc
                                TASK_UNINTERRUPTIBLE);
                spin_unlock_irq(&tsadc->reg_lock);

-               schedule();
+               schedule_timeout(usecs_to_jiffies(GET_ADC_TIMEOUT_US));

                spin_lock_irq(&tsadc->reg_lock);
                finish_wait(&tsadc->reg_se_wait, &wait);

I change function schedule with schedule_timeout, in case the ADC does not running (ie not powered) adc driver return -EAGAIN (no hang system)

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AM335x ADC hangs SDK8