+/*
+ * Wait while BB-bit doesn't reflect the I2C bus state
+ *
+ * In a multimaster environment, after IP software reset, BB-bit value doesn't
+ * correspond to the current bus state. It may happen what BB-bit will be 0,
+ * while the bus is busy due to another I2C master activity.
+ * Here are BB-bit values after reset:
+ * SDA SCL BB NOTES
+ * 0 0 0 1, 2
+ * 1 0 0 1, 2
+ * 0 1 1
+ * 1 1 0 3
+ * Later, if IP detect SDA=0 and SCL=1 (ACK) or SDA 1->0 while SCL=1 (START)
+ * combinations on the bus, it set BB-bit to 1.
+ * If IP detect SDA 0->1 while SCL=1 (STOP) combination on the bus,
+ * it set BB-bit to 0 and BF to 1.
+ * BB and BF bits correctly tracks the bus state while IP is suspended
+ * BB bit became valid on the next FCLK clock after CON_EN bit set
+ *
+ * NOTES:
+ * 1. Any transfer started when BB=0 and bus is busy wouldn't be
+ * completed by IP and results in controller timeout.
+ * 2. Any transfer started when BB=0 and SCL=0 results in IP
+ * starting to drive SDA low. In that case IP corrupt data
+ * on the bus.
+ * 3. Any transfer started in the middle of another master's transfer
+ * results in unpredictable results and data corruption
+ */
+static int omap_i2c_wait_for_bb_valid(struct omap_i2c_dev *dev)
+{
+ unsigned long bus_free_timeout = 0;
+ unsigned long timeout;
+ int bus_free = 0;
+ u16 stat, systest;
+
+ if (dev->bb_valid)
+ return 0;
+
+ timeout = jiffies + OMAP_I2C_TIMEOUT;
+ while (1) {
+ stat = omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG);
+ /*
+ * We will see BB or BF event in a case IP had detected any
+ * activity on the I2C bus. Now IP correctly tracks the bus
+ * state. BB-bit value is valid.
+ */
+ if (stat & (OMAP_I2C_STAT_BB | OMAP_I2C_STAT_BF))
+ break;
+
+ /*
+ * Otherwise, we must look signals on the bus to make
+ * the right decision.
+ */
+ systest = omap_i2c_read_reg(dev, OMAP_I2C_SYSTEST_REG);
+ if ((systest & OMAP_I2C_SYSTEST_SCL_I_FUNC) &&
+ (systest & OMAP_I2C_SYSTEST_SDA_I_FUNC)) {
+ if (!bus_free) {
+ bus_free_timeout = jiffies +
+ OMAP_I2C_BUS_FREE_TIMEOUT;
+ bus_free = 1;
+ }
+
+ /*
+ * SDA and SCL lines was high for 10 ms without bus
+ * activity detected. The bus is free. Consider
+ * BB-bit value is valid.
+ */
+ if (time_after(jiffies, bus_free_timeout))
+ break;
+ } else {
+ bus_free = 0;
+ }
+
+ if (time_after(jiffies, timeout)) {
+ dev_warn(dev->dev, "timeout waiting for bus ready\n");
+ return -ETIMEDOUT;
+ }
+
+ msleep(1);
+ }
+
+ dev->bb_valid = 1;
+ return 0;
+}
+