Re: Configuration of MAX7301

[Vikram Narayanan <vikram186-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

These are the changes I have done in my board file to make the max7301 work
with S3C24xx spi driver.

static struct s3c2410_spi_info mini2440_spi0_platdata = {
    .pin_cs = S3C2410_GPG(2),
    .num_cs = 1,
    .bus_num = 0,
};

static struct max7301_platform_data max7301_info = {
    .base = -1,
};
// The base is set as -1 since from max7301.c there is a call to
gpiochip_add, which would return if there is no base set.
>From the comment in the drivers/gpio/gpiolib.c

 <http://lxr.linux.no/linux+*/drivers/gpio/gpiolib.c#L912>If
chip->base is negative, this requests dynamic assignment of
<http://lxr.linux.no/linux+*/drivers/gpio/gpiolib.c#L913>a range of
valid GPIOs.

static struct spi_board_info mini2440_spi_board_info[] __initdata = {
    {
        .modalias    = "max7301",
        .platform_data    = &max7301_info,
        .max_speed_hz    = 13000000,
        .bus_num    = 0,
        .chip_select    = 0,
        .mode        = SPI_MODE_0,
    },
};

And from board init I am configuring the pins for SPI

    s3c2410_gpio_cfgpin(S3C2410_GPE(11), S3C2410_GPE11_SPIMISO0);
    s3c2410_gpio_cfgpin(S3C2410_GPE(12), S3C2410_GPE12_SPIMOSI0);
    s3c2410_gpio_cfgpin(S3C2410_GPE(13), S3C2410_GPE13_SPICLK0);
    s3c2410_gpio_pullup(S3C2410_GPE(11), 0);
    s3c2410_gpio_pullup(S3C2410_GPE(13), 0);
    s3c2410_gpio_cfgpin(S3C2410_GPG(2), S3C2410_GPIO_OUTPUT);
    s3c_device_spi0.dev.platform_data = &mini2440_spi0_platdata;
    spi_register_board_info(mini2440_spi_board_info,
        ARRAY_SIZE(mini2440_spi_board_info));

And in the max7301.c I have changed the
spi->bits_per_word = 8;

as my SPI master driver would not initialize the value isn't equal to 8.

When I insert the max7301 module now, I am getting error which traces back
to the file drivers/gpio/gpiolib.c

    if (status)
        pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
            chip->base, chip->base + chip->ngpio - 1,
            chip->label ? : "generic");

gpiochip add: gpios -1...26 (max7301) not registered.

I don't get a clear picture of what is wrong with the SPI configuration I
have done.
Can someone help me understanding what is wrong?

On Thu, Mar 3, 2011 at 4:37 PM, Jassi Brar <jassisinghbrar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> On Thu, Mar 3, 2011 at 2:57 AM, Vikram Narayanan <vikram186-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> wrote:
> > Hi,
> >
> > I am trying to interface the MAX7301 IC with my Samsung S3C2440
> processor.
> > The problem is the S3c supports only 8 bit word length for SPI transfer,
> > whereas my MAX requires 16 bit word length.
> > I couldn't find any info on the datasheet to use the IC on a 8 bit word
> > length. can i make the max7301_write function,
> >
> > static int max7301_write(struct spi_device *spi, unsigned int reg,
> unsigned
> > int val)
> > {
> >    u8 command = reg & 0x7F;
> >    u8 data = val & 0xFF;
> >    spi_write(spi, (const u8*)&command, sizeof(command));
> >    spi_write(spi, (const u8*)&data, sizeof(data));
> >    return 0;
> > }
> >
> > Will this make the IC work? Please share your ideas.
>
> If MAX7301 does require exactly 16bpw, typecasting wouldn't do.
>
> For simple control purposes, one option is to use the SPI pins with
> the common bit-banging driver.
>
> > --
> > Regards
> > Vikram
> >
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