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GPIO not working.

Gennadiy Kiryukhin
Expert 2800 points

One of the GPIO pins on my dm355 board is connected to a reset pin on my CMOS sensor. I tried the following two commands to deassert a reset signal. I tried those commands in arch/arm-mach-davinci/board-dm355-evm.c. The output stayed low. I also tried them in the mt9t031.c and had the same result.

    gpio_request(80, "MT9T_RESET");
    gpio_direction_output(80, 1); // reset high (deasserted)

What is the proper way to control the GPIOs?

  • 0
    Expert 2800 points

    Any ideas or comments? Thanks.

     

  • 0 in reply to Gennadiy Kiryukhin
    Expert 2800 points

    Got it working. Just like several posts on this forum mentioned, the PINMUX configuration was not set properly.

    Here is the code.

       void __iomem *pinmux;

        pinmux = (void __iomem *) IO_ADDRESS(DAVINCI_SYSTEM_MODULE_BASE + 0x4);
            __raw_writel( __raw_readl(pinmux) & 0xFFFFFFFC, pinmux);

    To set the correct pin as GPIO make sure to change the offset (0x4 for MINMUX1; in the second line) to refer to correct value and change the mask (0xFFFFFFFC for GIO81; in the third line) to clear the proper bits.

    For some reason gpio_request and gpio_direction_output do not change PINMUX registers. What is the point in having gpio_request functions if you can still have to do manual PINMUX configuration?