Re: [PATCH/RFC 1/1] recover from davinci i2c time out conditions

[David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>]

On Wednesday 15 July 2009, Philby John wrote:
>  /*
> + * Configure the i2c data pin as a GPIO input and the i2c clock pin as a
> + * high GPIO output.
> + */
> +static void disable_i2c_pins(void)
> +{
> +       unsigned long flags;
> +
> +       local_irq_save(flags);
> +       if (cpu_is_davinci_dm355()) {
> +               gpio_direction_input(15);
> +               gpio_direction_output(14, 0);
> +               gpio_set_value(14, 1);

As noted:  gpio_direction_output(14, 1) is better.

> +               davinci_cfg_reg(DM355_I2C_SDA);
> +               davinci_cfg_reg(DM355_I2C_SCL);
> +       }
> +       local_irq_restore(flags);
> +}
> +
> +/* Connect the i2c pins to the i2c controller. */
> +static void enable_i2c_pins(void)
> +{
> +       unsigned long flags;
> +
> +       local_irq_save(flags);
> +       if (cpu_is_davinci_dm355()) {
> +               davinci_cfg_reg(DM355_I2C_SDA);
> +               davinci_cfg_reg(DM355_I2C_SCL);
> +       }
> +       local_irq_restore(flags);
> +}
> +
> +
> +/* Generate a pulse on the i2c clock pin. */
> +static void pulse_i2c_clock(void)
> +{
> +       if (cpu_is_davinci_dm355()) {
> +               gpio_set_value(14, 0);
> +               udelay(20);
> +               gpio_set_value(14, 1);
> +               udelay(20);
> +       }
> +}
> +

The general problem with how that's done is that the SoC-specific
bits should not be in this file.  The mach-davinc/dm355.c file
should hold that configuration; likewise for other SoCs.


> +                       /* Disable i2c */
> +                       disable_i2c_pins();
> +                       for (i = 0; i < 10; i++)
> +                               pulse_i2c_clock();
> +                       /* Re-enable i2c */
> +                       enable_i2c_pins();

A better description of this is that you're trying to follow
the I2Cv3 instructions about how to *reset* the bus, yes?

> +                       i2c_davinci_init(dev);
>