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Conversion not completing in imx_adc driver

Question asked by Ed Krohne on Oct 29, 2012
Latest reply on Jan 18, 2013 by Don Snedigar
Branched to a new discussion

I'm trying to use the internal ADC driver in the imx-25. I'm running Linux 2.6.31 with the mxc additions. I've been able to configure the driver as a module, rebuild the kernel, and modules, and install the module.


The device (/dev/imx_adc) shows up and I'm able to issue the "init" and "deinit" ioctls. However, when trying to get a conversion of the general purpose channel 0, the driver initially hung; and the system required a hard reset to recover. Looking at the driver code, there are two while loops waiting on specific status events. I added some code to time out in 10 jiffies (100ms), and print out which of the loops got aborted. What isn't happening is the EOQ status bit is never getting set.


I've included the snippet from imx_adc_read_general below with my changes and debug statements:


enum IMX_ADC_STATUS imx_adc_read_general(unsigned short *result)
        unsigned long reg;
        unsigned int data_num = 0;
        unsigned long start;

        reg = __raw_readl(tsc_base + GCQCR);
        reg |= CQCR_FQS;
        __raw_writel(reg, tsc_base + GCQCR);

        pr_debug("  GCQCR = %08X\n", __raw_readl(tsc_base + GCQCR));
        pr_debug("  GCC0  = %08X\n", __raw_readl(tsc_base + GCC0));

        start = jiffies;

        while (!(__raw_readl(tsc_base + GCQSR) & CQSR_EOQ))
                if (jiffies == start + 10)
                        pr_debug("  GCQSR = %08X\n", __raw_readl(tsc_base + GCQSR));
                        pr_debug("  aborting EOQ loop\n");


After trying a conversion I get the following output from dmesg:


root@ublnx-arm-base:/lib/modules/2.6.31-SBT/kernel/drivers/mxc/adc# dmesg

imx_adc : imx_adc_open()

init adc


MXC_CCM_CCTL = 2103C0008

convert adc


  GCQCR = 00000F06

  GCC0  = 100317DC

  GCQSR = 00002000

  aborting EOQ loop

deinit adc


imx_adc : imx_adc_free()


Can anyone help with this. Has anyone ever successfully gotten a general purpose input to convert?