static int pca_init()

in algos/i2c-algo-pca.c [391:527]

• 107 lines of code
• 17 McCabe index (conditional complexity)

static int pca_init(struct i2c_adapter *adap)
{
	struct i2c_algo_pca_data *pca_data = adap->algo_data;

	adap->algo = &pca_algo;

	if (pca_probe_chip(adap) == I2C_PCA_CHIP_9564) {
		static int freqs[] = {330, 288, 217, 146, 88, 59, 44, 36};
		int clock;

		if (pca_data->i2c_clock > 7) {
			switch (pca_data->i2c_clock) {
			case 330000:
				pca_data->i2c_clock = I2C_PCA_CON_330kHz;
				break;
			case 288000:
				pca_data->i2c_clock = I2C_PCA_CON_288kHz;
				break;
			case 217000:
				pca_data->i2c_clock = I2C_PCA_CON_217kHz;
				break;
			case 146000:
				pca_data->i2c_clock = I2C_PCA_CON_146kHz;
				break;
			case 88000:
				pca_data->i2c_clock = I2C_PCA_CON_88kHz;
				break;
			case 59000:
				pca_data->i2c_clock = I2C_PCA_CON_59kHz;
				break;
			case 44000:
				pca_data->i2c_clock = I2C_PCA_CON_44kHz;
				break;
			case 36000:
				pca_data->i2c_clock = I2C_PCA_CON_36kHz;
				break;
			default:
				printk(KERN_WARNING
					"%s: Invalid I2C clock speed selected."
					" Using default 59kHz.\n", adap->name);
			pca_data->i2c_clock = I2C_PCA_CON_59kHz;
			}
		} else {
			printk(KERN_WARNING "%s: "
				"Choosing the clock frequency based on "
				"index is deprecated."
				" Use the nominal frequency.\n", adap->name);
		}

		clock = pca_clock(pca_data);
		printk(KERN_INFO "%s: Clock frequency is %dkHz\n",
		     adap->name, freqs[clock]);

		/* Store settings as these will be needed when the PCA chip is reset */
		pca_data->bus_settings.clock_freq = clock;

		pca_reset(pca_data);
	} else {
		int clock;
		int mode;
		int tlow, thi;
		/* Values can be found on PCA9665 datasheet section 7.3.2.6 */
		int min_tlow, min_thi;
		/* These values are the maximum raise and fall values allowed
		 * by the I2C operation mode (Standard, Fast or Fast+)
		 * They are used (added) below to calculate the clock dividers
		 * of PCA9665. Note that they are slightly different of the
		 * real maximum, to allow the change on mode exactly on the
		 * maximum clock rate for each mode
		 */
		int raise_fall_time;

		if (pca_data->i2c_clock > 1265800) {
			printk(KERN_WARNING "%s: I2C clock speed too high."
				" Using 1265.8kHz.\n", adap->name);
			pca_data->i2c_clock = 1265800;
		}

		if (pca_data->i2c_clock < 60300) {
			printk(KERN_WARNING "%s: I2C clock speed too low."
				" Using 60.3kHz.\n", adap->name);
			pca_data->i2c_clock = 60300;
		}

		/* To avoid integer overflow, use clock/100 for calculations */
		clock = pca_clock(pca_data) / 100;

		if (pca_data->i2c_clock > I2C_MAX_FAST_MODE_PLUS_FREQ) {
			mode = I2C_PCA_MODE_TURBO;
			min_tlow = 14;
			min_thi  = 5;
			raise_fall_time = 22; /* Raise 11e-8s, Fall 11e-8s */
		} else if (pca_data->i2c_clock > I2C_MAX_FAST_MODE_FREQ) {
			mode = I2C_PCA_MODE_FASTP;
			min_tlow = 17;
			min_thi  = 9;
			raise_fall_time = 22; /* Raise 11e-8s, Fall 11e-8s */
		} else if (pca_data->i2c_clock > I2C_MAX_STANDARD_MODE_FREQ) {
			mode = I2C_PCA_MODE_FAST;
			min_tlow = 44;
			min_thi  = 20;
			raise_fall_time = 58; /* Raise 29e-8s, Fall 29e-8s */
		} else {
			mode = I2C_PCA_MODE_STD;
			min_tlow = 157;
			min_thi  = 134;
			raise_fall_time = 127; /* Raise 29e-8s, Fall 98e-8s */
		}

		/* The minimum clock that respects the thi/tlow = 134/157 is
		 * 64800 Hz. Below that, we have to fix the tlow to 255 and
		 * calculate the thi factor.
		 */
		if (clock < 648) {
			tlow = 255;
			thi = 1000000 - clock * raise_fall_time;
			thi /= (I2C_PCA_OSC_PER * clock) - tlow;
		} else {
			tlow = (1000000 - clock * raise_fall_time) * min_tlow;
			tlow /= I2C_PCA_OSC_PER * clock * (min_thi + min_tlow);
			thi = tlow * min_thi / min_tlow;
		}

		/* Store settings as these will be needed when the PCA chip is reset */
		pca_data->bus_settings.mode = mode;
		pca_data->bus_settings.tlow = tlow;
		pca_data->bus_settings.thi = thi;

		pca_reset(pca_data);

		printk(KERN_INFO
		     "%s: Clock frequency is %dHz\n", adap->name, clock * 100);
	}
	udelay(500); /* 500 us for oscillator to stabilise */

	return 0;
}