[U-Boot-Users] [PATCH 1/1] Fix I2C for m547x/548x and m5445x processors.

[Wolfgang Denk]

In message <1215439715-28742-2-git-send-email-luigi.mantellini at idf-hit.com> you wrote:
> ---
>  drivers/i2c/fsl_i2c.c |   68 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 68 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
> index 0690340..8fd73c0 100644
> --- a/drivers/i2c/fsl_i2c.c
> +++ b/drivers/i2c/fsl_i2c.c
> @@ -78,6 +78,73 @@ static const struct fsl_i2c *i2c_dev[2] = {
>   * register.  See the application note AN2919 "Determining the I2C Frequency
>   * Divider Ratio for SCL"
>   */
> +#if defined(CONFIG_MCF547x_8x) || defined(CONFIG_MCF5445x)
> +static const struct {
> +	u8 fdr;
> +	unsigned short divider;
> +} fsl_i2c_speed_map[] = {
> +	  {.fdr=0x20, .divider=  20},   {.fdr=0x21, .divider=  22},   {.fdr=0x22, .divider=  24},
> +	  {.fdr=0x23, .divider=  26},   {.fdr=0x00, .divider=  28},   {.fdr=0x24, .divider=  28},
> +	  {.fdr=0x01, .divider=  30},   {.fdr=0x25, .divider=  32},   {.fdr=0x02, .divider=  34},
> +	  {.fdr=0x26, .divider=  36},   {.fdr=0x03, .divider=  40},   {.fdr=0x27, .divider=  40},
> +	  {.fdr=0x04, .divider=  44},   {.fdr=0x05, .divider=  48}, /*{.fdr=0x28, .divider=  48},*/
> +	  {.fdr=0x06, .divider=  56}, /*{.fdr=0x29, .divider=  56},*/ {.fdr=0x2A, .divider=  64},
> +	  {.fdr=0x07, .divider=  68},   {.fdr=0x2B, .divider=  72},   {.fdr=0x08, .divider=  80},
> +	/*{.fdr=0x2C, .divider=  80},*/ {.fdr=0x09, .divider=  88},   {.fdr=0x2D, .divider=  96},
> +	  {.fdr=0x0A, .divider= 104},   {.fdr=0x2E, .divider= 112},   {.fdr=0x0B, .divider= 128},
> +	/*{.fdr=0x2F, .divider= 128},*/ {.fdr=0x0C, .divider= 144},   {.fdr=0x0D, .divider= 160},
> +	/*{.fdr=0x30, .divider= 160},*/ {.fdr=0x0E, .divider= 192}, /*{.fdr=0x31, .divider= 192},*/
> +	  {.fdr=0x32, .divider= 224},   {.fdr=0x0F, .divider= 240},   {.fdr=0x33, .divider= 256},
> +	  {.fdr=0x10, .divider= 288},   {.fdr=0x11, .divider= 320}, /*{.fdr=0x34, .divider= 320},*/
> +	  {.fdr=0x12, .divider= 384}, /*{.fdr=0x35, .divider= 384},*/ {.fdr=0x36, .divider= 448},
> +	/*{.fdr=0x13, .divider= 480},*/ {.fdr=0x37, .divider= 512},   {.fdr=0x14, .divider= 576},
> +	  {.fdr=0x15, .divider= 640}, /*{.fdr=0x38, .divider= 640},*/ {.fdr=0x16, .divider= 768},
> +	/*{.fdr=0x39, .divider= 768},*/ {.fdr=0x3A, .divider= 896},   {.fdr=0x17, .divider= 960},
> +	  {.fdr=0x3B, .divider=1024},   {.fdr=0x18, .divider=1152},   {.fdr=0x19, .divider=1280},
> +	/*{.fdr=0x3C, .divider=1280},*/ {.fdr=0x1A, .divider=1536}, /*{.fdr=0x3D, .divider=1536},*/
> +	  {.fdr=0x3E, .divider=1792},   {.fdr=0x1B, .divider=1920},   {.fdr=0x3F, .divider=2048},
> +	  {.fdr=0x1C, .divider=2304},   {.fdr=0x1D, .divider=2560},   {.fdr=0x1E, .divider=3072},
> +	  {.fdr=0x1F, .divider=3840},   {.fdr=0x00, .divider=-1}
> +};
> +
> +/**
> + * Set the I2C bus speed for a given I2C device
> + *
> + * @param dev: the I2C device
> + * @i2c_clk: I2C bus clock frequency
> + * @speed: the desired speed of the bus
> + *
> + * The I2C device must be stopped before calling this function.
> + *
> + * The return value is the actual bus speed that is set.
> + */
> +static unsigned int set_i2c_bus_speed(const struct fsl_i2c *dev,
> +	unsigned int i2c_clk, unsigned int speed)
> +{
> +	unsigned short divider = min(i2c_clk / speed, (unsigned short) -1);
> +	unsigned int i;
> +	u8 fdr = 0;
> +
> +	/*
> +	 * We want to choose an FDR/DFSR that generates an I2C bus speed that
> +	 * is equal to or lower than the requested speed.  That means that we
> +	 * want the first divider that is equal to or greater than the
> +	 * calculated divider.
> +	 */
> +
> +	for (i = 0; i < ARRAY_SIZE(fsl_i2c_speed_map); i++)
> +		if (fsl_i2c_speed_map[i].divider >= divider) {
> +			fdr = fsl_i2c_speed_map[i].fdr;
> +			speed = i2c_clk / fsl_i2c_speed_map[i].divider;
> +			break;
> +		}
> +
> +	writeb(fdr, &dev->fdr);			/* set bus speed */
> +
> +	return speed;
> +}
> +#else /* ! (defined(CONFIG_MCF547x_8x) || defined(CONFIG_MCF5445x) */
> +

What a nightmare of data and code. So many magic numbers, so much
potential for errors. And for what?  Just for I2C support in U-Boot?

Are you really sure you don't simply want to use the bit-banging
driver?

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Committee, n.:  A group of men who individually can do nothing but as
a group decide that nothing can be done.                 - Fred Allen