i.mx6Q custom board, keep interrupt and hang.

[wallyyeh]

Hi, all:

    our product using i.mx6Q custom board. SDK_3.0.35_4.1.0_GA

recently some board boot without HDMI monitor attached will cause a endless loop of interruption.

I add some printk in kernel/driver/video/mxc_hdmi.c

    static irqreturn_t mxc_hdmi_hotplug( )

the kernel will enter this function, when it check (intr_stat & HDMI_IH_PHY_STAT0_HPD) will not matched (sometimes intr_stat is 0x2 or 0x0)

so it just leave interrupt function, and trigger by GIC again. and never stop.

I read reference manual chapter 3, there are 159 interruption in i.mx6Q , does all these trigger all interruption function in kernel?

the weird thing is if I booting with HDMI attached, I won't get this problem.

[wallyyeh]

It's been a long time,  and we find a workarround to this weird interrupt issue, initialize first before mxc_hdmi_disp_init() call request_irq().

following is what we add in mxc_hdmi_disp_init() in kernel/driver/video/mxc_hdmi.c:

/* initialize first, workarround for boot without DVI attached hang up*/

  mxc_hdmi_setup(hdmi, 0);

  mxc_hdmi_enable_video_path(hdmi);

  mxc_hdmi_cable_connected(hdmi);

#ifdef CONFIG_MXC_HDMI_CEC

  mxc_hdmi_cec_handle(0x80);

#endif

  hdmi_set_cable_state(1);

[igorpadykov]

Hi Wally

without HDMI monitor attached, signal

HDMI_HPD - HPD input analog comparator

is floating, so it can endlessly send erratic signal (

as connect/disconnect). You should fix it to static level.

Best regards

chip

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[wallyyeh]

Hi, chip! old friend, glad to see you again. :smileyhappy:

our HDMI_HPD is attached with a output from a OPA(operator amplifier), and value is 0.04v(HDMI not attached) and 3.3v(HDMI attached).

you mention there's a analog comparator inside the HDMI_HPD pin. so maybe 0.04v caused erratic signal?

[igorpadykov]

Hi Wally

probably OPA(operator amplifier) is broken,

since this is sensitive device. Just for test one

can repalce it on bad boards.

Best regards

chip

[AllenLai]

Hi Chp,

We sure the OPA(operator amplifier) is OK,

becaue we measure the voltage of HDMI_HPD is alaways low (<0.04V) without (HDMI not attached) by oscilloscope.

Even if we short HDMI_HPD to GND forcibly, the system also will cause a endless loop of interruption.

The failure rate is 11pcs/240pcs.

Thanks.

Allen

[igorpadykov]

Hi Wally

it may be the case that OPA (operator amplifier) is broken

and somehow damaged i.MX6 HDMI_HPD input.

Suggest to replace for test.

Best regards

chip

[wallyyeh]

Thanks, Chip.

I'll see if we can replace the soc and see if this issue resolved or not. :smileylaugh: