[U-Boot] [PATCH 3/3] fsl_i2c: Impl. AN2919, rev 5 to calculate FDR/DFSR

Wolfgang Grandegger
2009-09-21T10:53:36Z

Hi Joakim,

Joakim Tjernlund wrote:
> The latest AN2919 has changed the way FDR/DFSR should be calculated.
> Update the driver according to spec. However, Condition 2
> is not accounted for as it is not clear how to do so.

I compared rev. 5 of AN2919 with rev. 3 and, as you pointed out, it puts
additional constraints on how to select dfsr and fdr. Especially dfsr
should not exceed a certain, frequency dependent value: dfsr <= 50 /
period-in-ns. Therefore, I expected problems with divider values from
the table which high dfsr values. I did your "=> date;date;date;date"
test on a MPC8548 board using dfsr=43 and fdr=7 but it did not fail.
According to the rev. 5, dfsr is not allowed to be greater than 8.
Your patch works fine on this board as well. I have no time for a more
thorough testing with different CPUs and frequencies. Anyhow...

> Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>

I realized some minor coding style issues, though. See below.

> ---
> drivers/i2c/fsl_i2c.c | 90 ++++++++++++++++++++++++++++++-------------------
> 1 files changed, 55 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c
> index 0c5f6be..78f21c7 100644
> --- a/drivers/i2c/fsl_i2c.c
> +++ b/drivers/i2c/fsl_i2c.c
> @@ -100,29 +100,9 @@ static const struct fsl_i2c *i2c_dev[2] = {
> */
> static const struct {
> unsigned short divider;
> -#ifdef __PPC__
> - u8 dfsr;
> -#endif
> u8 fdr;
> } fsl_i2c_speed_map[] = {
> -#ifdef __PPC__
> - {160, 1, 32}, {192, 1, 33}, {224, 1, 34}, {256, 1, 35},
> - {288, 1, 0}, {320, 1, 1}, {352, 6, 1}, {384, 1, 2}, {416, 6, 2},
> - {448, 1, 38}, {480, 1, 3}, {512, 1, 39}, {544, 11, 3}, {576, 1, 4},
> - {608, 22, 3}, {640, 1, 5}, {672, 32, 3}, {704, 11, 5}, {736, 43, 3},
> - {768, 1, 6}, {800, 54, 3}, {832, 11, 6}, {896, 1, 42}, {960, 1, 7},
> - {1024, 1, 43}, {1088, 22, 7}, {1152, 1, 8}, {1216, 43, 7}, {1280, 1, 9},
> - {1408, 22, 9}, {1536, 1, 10}, {1664, 22, 10}, {1792, 1, 46},
> - {1920, 1, 11}, {2048, 1, 47}, {2176, 43, 11}, {2304, 1, 12},
> - {2560, 1, 13}, {2816, 43, 13}, {3072, 1, 14}, {3328, 43, 14},
> - {3584, 1, 50}, {3840, 1, 15}, {4096, 1, 51}, {4608, 1, 16},
> - {5120, 1, 17}, {6144, 1, 18}, {7168, 1, 54}, {7680, 1, 19},
> - {8192, 1, 55}, {9216, 1, 20}, {10240, 1, 21}, {12288, 1, 22},
> - {14336, 1, 58}, {15360, 1, 23}, {16384, 1, 59}, {18432, 1, 24},
> - {20480, 1, 25}, {24576, 1, 26}, {28672, 1, 62}, {30720, 1, 27},
> - {32768, 1, 63}, {36864, 1, 28}, {40960, 1, 29}, {49152, 1, 30},
> - {61440, 1, 31}, {-1, 1, 31}
> -#elif defined(__M68K__)
> +#ifdef __M68K__
> {20, 32}, {22, 33}, {24, 34}, {26, 35},
> {28, 0}, {28, 36}, {30, 1}, {32, 37},
> {34, 2}, {36, 38}, {40, 3}, {40, 39},
> @@ -158,7 +138,6 @@ 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;
>
> /*
> * We want to choose an FDR/DFSR that generates an I2C bus speed that
> @@ -166,31 +145,72 @@ static unsigned int set_i2c_bus_speed(const struct fsl_i2c *dev,
> * 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) {
> - u8 fdr;
> #ifdef __PPC__
> - u8 dfsr;
> + u8 dfsr, fdr = 0x31; /* Default if no FDR found */
> + /* a, b and dfsr matches identifiers A,B and C respectively in AN2919 */
> + unsigned short a, b, ga, gb;
> + unsigned long c_div, est_div;
> +
> #ifdef CONFIG_FSL_I2C_CUSTOM_DFSR
> - dfsr = CONFIG_FSL_I2C_CUSTOM_DFSR;
> + dfsr = CONFIG_FSL_I2C_CUSTOM_DFSR;
> #else
> - dfsr = fsl_i2c_speed_map[i].dfsr;
> -#endif
> - writeb(dfsr, &dev->dfsrr); /* set default filter */
> + /* Condition 1: dfsr <= 50/T */
> + dfsr = (5 * (i2c_clk / 1000)) / 100000;
> #endif
> #ifdef CONFIG_FSL_I2C_CUSTOM_FDR
> - fdr = CONFIG_FSL_I2C_CUSTOM_FDR;
> - speed = i2c_clk / divider; /* Fake something */
> + fdr = CONFIG_FSL_I2C_CUSTOM_FDR;
> + speed = i2c_clk / divider; /* Fake something */
> #else
> + debug("Requested speed:%d, i2c_clk:%d\n", speed, i2c_clk);
> + if (!dfsr)
> + dfsr = 1;
> +
> + est_div = ~0;
> + for (ga = 0x4, a = 10; a <= 30; ga++, a += 2) {
> + for (gb = 0; gb < 8; gb++) {
> + b = 16 << gb;
> + c_div = b * (a + ((3*dfsr)/b)*2);

Please use spaces around "/" and "*".

> + if ((c_div > divider) && (c_div < est_div)) {
> + unsigned short bin_gb, bin_ga;
> +
> + est_div = c_div;
> + bin_gb = gb << 2;
> + bin_ga = (ga & 0x3) | ((ga & 0x4) << 3);
> + fdr = bin_gb | bin_ga;
> + speed = i2c_clk / est_div;
> + debug("FDR:0x%.2x, div:%ld, ga:0x%x, gb:0x%x, "
> + "a:%d, b:%d, speed:%d\n",
> + fdr, est_div, ga, gb, a, b, speed);
> + /* Condition 2 not accounted for */
> + debug("Tr <= %d ns\n",

Please remove trailing white space.

Wolfgang.