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MAX3100 (SPI to UART bridge) driver not working

Added by Zhe Ji over 9 years ago

Hello,

We are trying to compile the driver for MAX3100 and we are unable to get the node /dev/ttyMAX in spite of these changes:

1. Changed baseboard-mityarm335x-devkit-3359.c to the following:

#include <linux/serial_max3100.h>
static __init void baseboard_setup_spi0_devices(void)
{
    setup_pin_mux(spi0_pin_mux);
    spi_register_board_info(baseboard_spi0_slave_info,
            ARRAY_SIZE(baseboard_spi0_slave_info));

    //baseboard_setup_audio();
    //baseboard_setup_ts();

}
static struct spi_board_info baseboard_spi0_slave_info[] = {
    {
        .modalias    = "spi:max3100",
        .controller_data = &spi0_ctlr_data,
        .platform_data    = &max3100_plat_data,
        .irq         = IRQ_EINT12,
        .max_speed_hz    = 5*1000*1000,
        .bus_num    = 0,
        .chip_select    = 0,
        .mode         = SPI_MODE_0,
    },

2. Went into Linux menuconfig and enabled support for MAX3100 chip (device drivers --> character devices --> serial --> MAX3100)

We changed the max3100.c to print some things in the boot log, and its says that the __init max3100_init(void) is being executed and is fine.

But we still can't see the "/dev"ttyMAX" it is supposed to create.

Any suggestions?

Bindu


Replies (3)

RE: MAX3100 (SPI to UART bridge) driver not working - Added by Jonathan Cormier over 9 years ago

The init driver gets called when the driver is added to the kernel. If its built in then this happens early on, if its built as a module then this happens when you insert the module. The probe function gets called when the driver gets tied to a device and thus should be getting called when you run the spi_register... call. If you aren't seeing the probe then that usually indicates your modalias is incorrect.

Looking at the max3100.c file and searching for a name string I get two possible names. "ttyMAX" and "max3100". If I recall correctly using the .driver.name wasn't the correct name for other drivers i've used in the past. So I would start by trying the "ttyMAX" name first. Make sure to check for your print statment in the max3100_probe function to verify if you've gotten the correct name.

  static struct uart_driver max3100_uart_driver = {
          .owner          = THIS_MODULE,
          .driver_name    = "ttyMAX",
          .dev_name       = "ttyMAX",
          .major          = MAX3100_MAJOR,
          .minor          = MAX3100_MINOR,
          .nr             = MAX_MAX3100,
  };
  static struct spi_driver max3100_driver = {
          .driver = {
                  .name           = "max3100",
                  .bus            = &spi_bus_type,
                  .owner          = THIS_MODULE,
          },

          .probe          = max3100_probe,
          .remove         = __devexit_p(max3100_remove),
          .suspend        = max3100_suspend,
          .resume         = max3100_resume,
  };

RE: MAX3100 (SPI to UART bridge) driver not working - Added by Bindu Jagannatha over 9 years ago

Jonathan,

Thank you for the answer; using the following helped with respect to creating the /dev/ttyMAX0:

static struct spi_board_info baseboard_spi0_slave_info[] = {
    {
        .modalias    = "max3100",
        .controller_data = &spi0_ctlr_data,
        .platform_data    = &max3100_plat_data,
        .irq         = -1,
        .max_speed_hz    = 5*1000*1000,
        .bus_num    = 1,
        .chip_select    = 1,
        .mode         = SPI_MODE_0,
    },

However, it goes into kernel oops when I try to test a small program on the port. Is it due to the value of .irq? How does one decide what value that should be (the max3100.c said use IRQ_EINT12, but that doesn't exist).

Bindu

RE: MAX3100 (SPI to UART bridge) driver not working - Added by Jonathan Cormier over 9 years ago

Bindu,

You can look at how the other baseboard_spi0_slave_info have the irq filled in. Its possible that simply not setting the value might be the correct action.

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