i.MX6ULL - LCD Reset / GPIO5_IO09 / Tamper

[brianptl]

Hi All,

I am investigating an issue with our custom board and I cannot seem to control the pad MX6_PAD_SNVS_TAMPER9__GPIO5_IO09 inside u-boot. I am using an LCD. It is a different LCD than on the 14x14 imx6ull dev kit, however the LCD pin configuration is the same on the dev kit.

I cannot seem to toggle the pin, either as a GPIO or through the LCD interface. It always appears high.

Ref 1: i.MX 6ULL Applications Processor Reference Manual, Rev. 1, 11/2017

I have done the following in u-boot:

Read SW_PAD_CTL_PAD_SNVS_TAMPER9 SW PAD Control Register, page 1541 (Ref 1)

Reg Address: 229_0070h

=> md 2290070  
02290070: 000110a0 00000000 00000000 00000000    ................

Looks like the default values.

Read SW_MUX_CTL_PAD_SNVS_TAMPER9 SW MUX Control Register, page 1508 (Ref 1)

Reg Address: 229_002Ch

=> md 229002C
0229002c: 00000000 000030a0 0001b0a0 0001b0a0    .....0..........

Writing has no effect:

=> mw.l 229002C 5
=> md 229002C    
0229002c: 00000000 000030a0 0001b0a0 0001b0a0    .....0..........

It does state that the value here depends on TAMPER_PIN_DISABLE[1:0]

So read the fuses:

=> fuse read 0 3
Reading bank 0:

Word 0x00000003: 71310098

Bits 21:20 are 11, so the tamper pins are used as GPIO according to the Fusemap Descriptions Table on page 228 (Ref 1)

Read GPIO direction register (GPIO5_GDIR) , page 1357 (Ref 1)

Reg Address: 20A_C004

=> md 20AC004
020ac004: 00000200 00000820 00000000 00000000    .... ...........

Bit 9 is set, so we have an output

Read GPIO data register (GPIO5_DR), page 1357 (Ref 1)

Reg Address: 20A_C000

=> md 20AC000
020ac000: 00000a20 00000200 00000820 00000000     ....... .......

Attempt to write, pin stays high:

=> mw.l 20AC000 820
=> md 20AC000      
020ac000: 00000820 00000200 00000820 00000000     ....... .......

Maybe the LCD module has control? Try a write of eLCDIF General Control1 Register (LCDIF_CTRL1), page 2171 (Ref 1)

Reg Address: 21C_8010h

Read first:

=> md 21C8010
021c8010: 00070300 00070300 00070300 00070300    ................

Try to toggle:

=> mw.l 21C8010 00070301
=> md 21C8010           
021c8010: 00070301 00070301 00070301 00070301    ................

But the pin is still high.

Any thoughts? I must be missing something obvious.

Thanks.

[igorpadykov]

Hi Brian

this may be hardware issue, one can try to toggle it with jtag,

may be useful to check baremetal sdk test (zip can be found on https://community.nxp.com/thread/432859 )

Best regards
igor
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[brianptl]

Hi Igor,

Thanks for the response.

It turns out the u-boot file u-boot-imx/board/freescale/mx6ullevk/mx6ullevk.c has a different pin for LCD reset than the one that is suggested in the schematic. I assumed the code was correct, which it does not appear to be.

The lines:

    /* LCD_RST */
    MX6_PAD_SNVS_TAMPER9__GPIO5_IO09 | MUX_PAD_CTRL(NO_PAD_CTRL),

and

    /* Reset the LCD */
    gpio_request(IMX_GPIO_NR(5, 9), "lcd reset");
    gpio_direction_output(IMX_GPIO_NR(5, 9) , 0);
    udelay(500);
    gpio_direction_output(IMX_GPIO_NR(5, 9) , 1);

misled me down the wrong path.

The GPIO that I actually needed was MX6_PAD_LCD_RESET__GPIO3_IO04

    /* LCD_RST */
    MX6_PAD_LCD_RESET__GPIO3_IO04 | MUX_PAD_CTRL(NO_PAD_CTRL),

    /* Reset the LCD */
    gpio_request(IMX_GPIO_NR(3, 4), "lcd reset");
    gpio_direction_output(IMX_GPIO_NR(3, 4) , 0);
    udelay(20);
    gpio_direction_output(IMX_GPIO_NR(3, 4) , 1);

Thanks,

Brian.

[shamiullah]

Hi Brian,

I am also using the same pin for lcd reset in my custom board. I changed in uboot, i am getting nxp logo in uboot stage but i am not able to see anything when kernel booting starts. Can you please let me know the issues you faced while configuring in kernel and device tree. I am getting black screen when kernel booting starts. Please let me know

With regards

Shamiullah