[U-Boot] [PATCH 3/4] i2c: cdns: Support different bus speeds

[Heiko Schocher]

Hello Michal,

Am 14.04.2016 um 14:15 schrieb Michal Simek:
> 400kHz is maximum freq which can be used on Xilinx ZynqMP.
> Support it with standard divider calculator.
> Input freq is hardcoded to 100MHz input freq till we have clock driver
> which can provide this information for exact configuration.
>
> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
> ---
>
>   drivers/i2c/i2c-cdns.c | 76 +++++++++++++++++++++++++++++++++++++++++++++-----
>   1 file changed, 69 insertions(+), 7 deletions(-)

just some nitpick, beside of this:

Reviewed-by: Heiko Schocher <hs at denx.de>

> diff --git a/drivers/i2c/i2c-cdns.c b/drivers/i2c/i2c-cdns.c
> index 0bc6aaaa6f90..5642cd91fe2e 100644
> --- a/drivers/i2c/i2c-cdns.c
> +++ b/drivers/i2c/i2c-cdns.c
> @@ -112,6 +112,7 @@ static void cdns_i2c_debug_status(struct cdns_i2c_regs *cdns_i2c)
>
>   struct i2c_cdns_bus {
>   	int id;
> +	unsigned int input_freq;
>   	struct cdns_i2c_regs __iomem *regs;	/* register base */
>   };
>
> @@ -133,20 +134,79 @@ static u32 cdns_i2c_wait(struct cdns_i2c_regs *cdns_i2c, u32 mask)
>   	return int_status & mask;
>   }
>
> +#define CDNS_I2C_DIVA_MAX	4
> +#define CDNS_I2C_DIVB_MAX	64
> +
> +static int cdns_i2c_calc_divs(unsigned long *f, unsigned long input_clk,
> +		unsigned int *a, unsigned int *b)
> +{
> +	unsigned long fscl = *f, best_fscl = *f, actual_fscl, temp;
> +	unsigned int div_a, div_b, calc_div_a = 0, calc_div_b = 0;
> +	unsigned int last_error, current_error;
> +
> +	/* calculate (divisor_a+1) x (divisor_b+1) */

please add a space before and after the "+"

> +	temp = input_clk / (22 * fscl);
> +
> +	/*
> +	 * If the calculated value is negative or 0CDNS_I2C_DIVA_MAX,
> +	 * the fscl input is out of range. Return error.
> +	 */
> +	if (!temp || (temp > (CDNS_I2C_DIVA_MAX * CDNS_I2C_DIVB_MAX)))
> +		return -EINVAL;
> +
> +	last_error = -1;
> +	for (div_a = 0; div_a < CDNS_I2C_DIVA_MAX; div_a++) {
> +		div_b = DIV_ROUND_UP(input_clk, 22 * fscl * (div_a + 1));
> +
> +		if ((div_b < 1) || (div_b > CDNS_I2C_DIVB_MAX))
> +			continue;
> +		div_b--;
> +
> +		actual_fscl = input_clk / (22 * (div_a + 1) * (div_b + 1));
> +
> +		if (actual_fscl > fscl)
> +			continue;
> +
> +		current_error = ((actual_fscl > fscl) ? (actual_fscl - fscl) :
> +							(fscl - actual_fscl));
> +
> +		if (last_error > current_error) {
> +			calc_div_a = div_a;
> +			calc_div_b = div_b;
> +			best_fscl = actual_fscl;
> +			last_error = current_error;
> +		}
> +	}
> +
> +	*a = calc_div_a;
> +	*b = calc_div_b;
> +	*f = best_fscl;
> +
> +	return 0;
> +}
> +
>   static int cdns_i2c_set_bus_speed(struct udevice *dev, unsigned int speed)
>   {
>   	struct i2c_cdns_bus *bus = dev_get_priv(dev);
> +	u32 div_a = 0, div_b = 0;
> +	unsigned long speed_p = speed;
> +	int ret = 0;
>
> -	if (speed != 100000) {
> -		printf("%s, failed to set clock speed to %u\n", __func__,
> -		       speed);
> +	if (speed > 400000) {
> +		debug("%s, failed to set clock speed to %u\n", __func__,
> +		      speed);
>   		return -EINVAL;
>   	}
>
> -	/* TODO: Calculate dividers based on CPU_CLK_1X */
> -	/* 111MHz / ( (3 * 17) * 22 ) = ~100KHz */
> -	writel((16 << CDNS_I2C_CONTROL_DIV_B_SHIFT) |
> -		(2 << CDNS_I2C_CONTROL_DIV_A_SHIFT), &bus->regs->control);
> +	ret = cdns_i2c_calc_divs(&speed_p, bus->input_freq, &div_a, &div_b);
> +	if (ret)
> +		return ret;
> +
> +	debug("%s: div_a: %d, div_b: %d, input freq: %d, speed: %d/%ld\n",
> +	      __func__, div_a, div_b, bus->input_freq, speed, speed_p);
> +
> +	writel((div_b << CDNS_I2C_CONTROL_DIV_B_SHIFT) |
> +	       (div_a << CDNS_I2C_CONTROL_DIV_A_SHIFT), &bus->regs->control);
>
>   	/* Enable master mode, ack, and 7-bit addressing */
>   	setbits_le32(&bus->regs->control, CDNS_I2C_CONTROL_MS |
> @@ -293,6 +353,8 @@ static int cdns_i2c_ofdata_to_platdata(struct udevice *dev)
>   	if (!i2c_bus->regs)
>   		return -ENOMEM;
>
> +	i2c_bus->input_freq = 100000000; /* TODO hardcode input freq for now */
> +
>   	return 0;
>   }
>
>

bye,
Heiko
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