I2C support for NXP LPC18xx family

Add support for the I2C controller found on several NXP devices including LPC2xxx, LPC178x/7x and LPC18xx/43xx. The controller is implemented as a state machine and the driver act upon the state changes when the bus is accessed.

The I2C controller supports master/slave operation, bus arbitration, programmable clock rate, and speeds up to 1 Mbit/s.

Signed-off-by Joachim Eastwood <[email protected]>

drivers/i2c/busses/i2c-lpc2k.c new file +13 -0

+static void i2c_lpc2k_pump_msg(struct lpc2k_i2c *i2c)
+{
+	unsigned char data;
+	u32 status;
+
+	/*
+	 * I2C in the LPC2xxx series is basically a state machine.
+	 * Just run through the steps based on the current status.
+	 */
+	status = readl(i2c->reg_base + LPC24XX_I2STAT);
+
+	switch (status) {
+	case M_START:

Quoted 9 lines · Joachim Eastwood

Add support for the I2C controller found on several NXP devices including LPC2xxx, LPC178x/7x and LPC18xx/43xx. The controller is implemented as a state machine and the driver act upon the state changes when the bus is accessed.

The I2C controller supports master/slave operation, bus arbitration, programmable clock rate, and speeds up to 1 Mbit/s.

Signed-off-by Joachim Eastwood <[email protected]>

Thanks for the submission! Looking mostly good already.

Quoted 21 lines

drivers/i2c/busses/i2c-lpc2k.c new file +21 -0

+static void i2c_lpc2k_pump_msg(struct lpc2k_i2c *i2c)
+{
+     unsigned char data;
+     u32 status;
+
+     /*
+      * I2C in the LPC2xxx series is basically a state machine.
+      * Just run through the steps based on the current status.
+      */
+     status = readl(i2c->reg_base + LPC24XX_I2STAT);
+
+     switch (status) {
+     case M_START:
+     case M_REPSTART:
+             /* Start bit was just sent out, send out addr and dir */
+             data = (i2c->msg->addr << 1);
+             if (i2c->msg->flags & I2C_M_RD)
+                     data |= 1;
+
+             writel(data, i2c->reg_base + LPC24XX_I2DAT);
+             writel(LPC24XX_STA, i2c->reg_base + LPC24XX_I2CONCLR);

Review

Quoted 2 lines

(quoted diff) +2 -0

+
+             dev_dbg(&i2c->adap.dev, "Start sent with addr 0x%02x\n", data);

I assume the driver is basically working. So, in my book, most of this debug output is useful when the driver was developed, not so much afterwards. Also, it is printed in interrupt context possibly causing latency. However, the information is useful for understanding the driver, so I'd suggest to convert them into comments?

drivers/i2c/busses/i2c-lpc2k.c line 474

Quoted 3 lines

drivers/i2c/busses/i2c-lpc2k.c new file +3 -0

+     i2c->adap.nr = pdev->id;
+
+     ret = i2c_add_numbered_adapter(&i2c->adap);

Intended? Most DT enabled drivers simply user i2c_add_adapter(). The core then takes care of aliases defined in DT.

And please have a look at Documentation/i2c/fault-codes. Arbitration Lost should be -EAGAIN, NACK should be -ENXIO, and so forth...