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Commit 2d0ef4fb authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 

Pull i2c fixes from Wolfram Sang:
 "i2c has a bugfix and documentation improvements for you"

* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  Documentation: i2c: mention ACPI method for instantiating devices
  Documentation: i2c: describe devicetree method for instantiating devices
  i2c: mv64xxx: refactor message start to ensure proper initialization
parents 5a667a0c fde1e418

Documentation/i2c/instantiating-devices

+39 −2
Original line number Diff line number Diff line
@@ -8,8 +8,8 @@ reason, the kernel code must instantiate I2C devices explicitly. There are 
several ways to achieve this, depending on the context and requirements.





Method 1: Declare the I2C devices by bus number

-----------------------------------------------

Method 1a: Declare the I2C devices by bus number

------------------------------------------------



This method is appropriate when the I2C bus is a system bus as is the case

for many embedded systems. On such systems, each I2C bus has a number
@@ -51,6 +51,43 @@ The devices will be automatically unbound and destroyed when the I2C bus 
they sit on goes away (if ever.)





Method 1b: Declare the I2C devices via devicetree

-------------------------------------------------



This method has the same implications as method 1a. The declaration of I2C

devices is here done via devicetree as subnodes of the master controller.



Example:



	i2c1: i2c@400a0000 {

		/* ... master properties skipped ... */

		clock-frequency = <100000>;



		flash@50 {

			compatible = "atmel,24c256";

			reg = <0x50>;

		};



		pca9532: gpio@60 {

			compatible = "nxp,pca9532";

			gpio-controller;

			#gpio-cells = <2>;

			reg = <0x60>;

		};

	};



Here, two devices are attached to the bus using a speed of 100kHz. For

additional properties which might be needed to set up the device, please refer

to its devicetree documentation in Documentation/devicetree/bindings/.





Method 1c: Declare the I2C devices via ACPI

-------------------------------------------



ACPI can also describe I2C devices. There is special documentation for this

which is currently located at Documentation/acpi/enumeration.txt.





Method 2: Instantiate the devices explicitly

--------------------------------------------

drivers/i2c/busses/i2c-mv64xxx.c

+14 −19
Original line number Diff line number Diff line
@@ -97,7 +97,6 @@ enum { 
enum {

	MV64XXX_I2C_ACTION_INVALID,

	MV64XXX_I2C_ACTION_CONTINUE,

	MV64XXX_I2C_ACTION_OFFLOAD_SEND_START,

	MV64XXX_I2C_ACTION_SEND_START,

	MV64XXX_I2C_ACTION_SEND_RESTART,

	MV64XXX_I2C_ACTION_OFFLOAD_RESTART,
@@ -204,6 +203,9 @@ static int mv64xxx_i2c_offload_msg(struct mv64xxx_i2c_data *drv_data) 
	unsigned long ctrl_reg;

	struct i2c_msg *msg = drv_data->msgs;



	if (!drv_data->offload_enabled)

		return -EOPNOTSUPP;



	drv_data->msg = msg;

	drv_data->byte_posn = 0;

	drv_data->bytes_left = msg->len;
@@ -433,8 +435,7 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data) 


		drv_data->msgs++;

		drv_data->num_msgs--;

		if (!(drv_data->offload_enabled &&

				mv64xxx_i2c_offload_msg(drv_data))) {

		if (mv64xxx_i2c_offload_msg(drv_data) < 0) {

			drv_data->cntl_bits |= MV64XXX_I2C_REG_CONTROL_START;

			writel(drv_data->cntl_bits,

			drv_data->reg_base + drv_data->reg_offsets.control);
@@ -458,15 +459,14 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data) 
			drv_data->reg_base + drv_data->reg_offsets.control);

		break;



	case MV64XXX_I2C_ACTION_OFFLOAD_SEND_START:

		if (!mv64xxx_i2c_offload_msg(drv_data))

			break;

		else

			drv_data->action = MV64XXX_I2C_ACTION_SEND_START;

		/* FALLTHRU */

	case MV64XXX_I2C_ACTION_SEND_START:

		/* Can we offload this msg ? */

		if (mv64xxx_i2c_offload_msg(drv_data) < 0) {

			/* No, switch to standard path */

			mv64xxx_i2c_prepare_for_io(drv_data, drv_data->msgs);

			writel(drv_data->cntl_bits | MV64XXX_I2C_REG_CONTROL_START,

				drv_data->reg_base + drv_data->reg_offsets.control);

		}

		break;



	case MV64XXX_I2C_ACTION_SEND_ADDR_1:
@@ -625,15 +625,10 @@ mv64xxx_i2c_execute_msg(struct mv64xxx_i2c_data *drv_data, struct i2c_msg *msg, 
	unsigned long	flags;



	spin_lock_irqsave(&drv_data->lock, flags);

	if (drv_data->offload_enabled) {

		drv_data->action = MV64XXX_I2C_ACTION_OFFLOAD_SEND_START;

		drv_data->state = MV64XXX_I2C_STATE_WAITING_FOR_START_COND;

	} else {

		mv64xxx_i2c_prepare_for_io(drv_data, msg);



	drv_data->action = MV64XXX_I2C_ACTION_SEND_START;

	drv_data->state = MV64XXX_I2C_STATE_WAITING_FOR_START_COND;

	}



	drv_data->send_stop = is_last;

	drv_data->block = 1;

	mv64xxx_i2c_do_action(drv_data);