+/* I2C speed map for a DFSR value of 1 */
+
+/*
+ * Map I2C frequency dividers to FDR and DFSR values
+ *
+ * This structure is used to define the elements of a table that maps I2C
+ * frequency divider (I2C clock rate divided by I2C bus speed) to a value to be
+ * programmed into the Frequency Divider Ratio (FDR) and Digital Filter
+ * Sampling Rate (DFSR) registers.
+ *
+ * The actual table should be defined in the board file, and it must be called
+ * fsl_i2c_speed_map[].
+ *
+ * The last entry of the table must have a value of {-1, X}, where X is same
+ * FDR/DFSR values as the second-to-last entry. This guarantees that any
+ * search through the array will always find a match.
+ *
+ * The values of the divider must be in increasing numerical order, i.e.
+ * fsl_i2c_speed_map[x+1].divider > fsl_i2c_speed_map[x].divider.
+ *
+ * For this table, the values are based on a value of 1 for the DFSR
+ * register. See the application note AN2919 "Determining the I2C Frequency
+ * Divider Ratio for SCL"
+ *
+ * ColdFire I2C frequency dividers for FDR values are different from
+ * PowerPC. The protocol to use the I2C module is still the same.
+ * A different table is defined and are based on MCF5xxx user manual.
+ *
+ */
+static const struct {
+ unsigned short divider;
+ u8 fdr;
+} fsl_i2c_speed_map[] = {
+#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},
+ {44, 4}, {48, 5}, {48, 40}, {56, 6},
+ {56, 41}, {64, 42}, {68, 7}, {72, 43},
+ {80, 8}, {80, 44}, {88, 9}, {96, 41},
+ {104, 10}, {112, 42}, {128, 11}, {128, 43},
+ {144, 12}, {160, 13}, {160, 48}, {192, 14},
+ {192, 49}, {224, 50}, {240, 15}, {256, 51},
+ {288, 16}, {320, 17}, {320, 52}, {384, 18},
+ {384, 53}, {448, 54}, {480, 19}, {512, 55},
+ {576, 20}, {640, 21}, {640, 56}, {768, 22},
+ {768, 57}, {960, 23}, {896, 58}, {1024, 59},
+ {1152, 24}, {1280, 25}, {1280, 60}, {1536, 26},
+ {1536, 61}, {1792, 62}, {1920, 27}, {2048, 63},
+ {2304, 28}, {2560, 29}, {3072, 30}, {3840, 31},
+ {-1, 31}
+#endif
+};
+
+/**
+ * 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);
+
+ /*
+ * 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.
+ */
+#ifdef __PPC__
+ 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;
+#else
+ /* 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 */
+#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);
+ 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",
+ (b - 3 * dfsr) * 1000000 /
+ (i2c_clk / 1000));
+ }
+ }
+ if (a == 20)
+ a += 2;
+ if (a == 24)
+ a += 4;
+ }
+ debug("divider:%d, est_div:%ld, DFSR:%d\n", divider, est_div, dfsr);
+ debug("FDR:0x%.2x, speed:%d\n", fdr, speed);
+#endif
+ writeb(dfsr, &dev->dfsrr); /* set default filter */
+ writeb(fdr, &dev->fdr); /* set bus speed */
+#else
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(fsl_i2c_speed_map); i++)
+ if (fsl_i2c_speed_map[i].divider >= divider) {
+ u8 fdr;
+
+ fdr = fsl_i2c_speed_map[i].fdr;
+ speed = i2c_clk / fsl_i2c_speed_map[i].divider;
+ writeb(fdr, &dev->fdr); /* set bus speed */
+
+ break;
+ }
+#endif
+ return speed;
+}
+