diff options
Diffstat (limited to 'Documentation/i2c')
-rw-r--r-- | Documentation/i2c/busses/i2c-i801 | 1 | ||||
-rw-r--r-- | Documentation/i2c/functionality | 2 | ||||
-rw-r--r-- | Documentation/i2c/i2c-protocol | 35 | ||||
-rw-r--r-- | Documentation/i2c/instantiating-devices | 41 |
4 files changed, 61 insertions, 18 deletions
diff --git a/Documentation/i2c/busses/i2c-i801 b/Documentation/i2c/busses/i2c-i801 index aaaf069306a3..adf5e33e8312 100644 --- a/Documentation/i2c/busses/i2c-i801 +++ b/Documentation/i2c/busses/i2c-i801 @@ -26,6 +26,7 @@ Supported adapters: * Intel Wellsburg (PCH) * Intel Coleto Creek (PCH) * Intel Wildcat Point-LP (PCH) + * Intel BayTrail (SOC) Datasheets: Publicly available at the Intel website On Intel Patsburg and later chipsets, both the normal host SMBus controller diff --git a/Documentation/i2c/functionality b/Documentation/i2c/functionality index b0ff2ab596ce..4556a3eb87c4 100644 --- a/Documentation/i2c/functionality +++ b/Documentation/i2c/functionality @@ -46,7 +46,7 @@ A few combinations of the above flags are also defined for your convenience: and write_block_data commands I2C_FUNC_SMBUS_I2C_BLOCK Handles the SMBus read_i2c_block_data and write_i2c_block_data commands - I2C_FUNC_SMBUS_EMUL Handles all SMBus commands than can be + I2C_FUNC_SMBUS_EMUL Handles all SMBus commands that can be emulated by a real I2C adapter (using the transparent emulation layer) diff --git a/Documentation/i2c/i2c-protocol b/Documentation/i2c/i2c-protocol index 0b3e62d1f77a..ff6d6cee6c7e 100644 --- a/Documentation/i2c/i2c-protocol +++ b/Documentation/i2c/i2c-protocol @@ -6,8 +6,8 @@ Key to symbols S (1 bit) : Start bit P (1 bit) : Stop bit Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0. -A, NA (1 bit) : Accept and reverse accept bit. -Addr (7 bits): I2C 7 bit address. Note that this can be expanded as usual to +A, NA (1 bit) : Accept and reverse accept bit. +Addr (7 bits): I2C 7 bit address. Note that this can be expanded as usual to get a 10 bit I2C address. Comm (8 bits): Command byte, a data byte which often selects a register on the device. @@ -49,11 +49,20 @@ a byte read, followed by a byte write: Modified transactions ===================== -The following modifications to the I2C protocol can also be generated, -with the exception of I2C_M_NOSTART these are usually only needed to -work around device issues: +The following modifications to the I2C protocol can also be generated by +setting these flags for i2c messages. With the exception of I2C_M_NOSTART, they +are usually only needed to work around device issues: - Flag I2C_M_NOSTART: +I2C_M_IGNORE_NAK: + Normally message is interrupted immediately if there is [NA] from the + client. Setting this flag treats any [NA] as [A], and all of + message is sent. + These messages may still fail to SCL lo->hi timeout. + +I2C_M_NO_RD_ACK: + In a read message, master A/NA bit is skipped. + +I2C_M_NOSTART: In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some point. For example, setting I2C_M_NOSTART on the second partial message generates something like: @@ -67,17 +76,13 @@ work around device issues: I2C device but may also be used between direction changes by some rare devices. - Flags I2C_M_REV_DIR_ADDR +I2C_M_REV_DIR_ADDR: This toggles the Rd/Wr flag. That is, if you want to do a write, but need to emit an Rd instead of a Wr, or vice versa, you set this flag. For example: S Addr Rd [A] Data [A] Data [A] ... [A] Data [A] P - Flags I2C_M_IGNORE_NAK - Normally message is interrupted immediately if there is [NA] from the - client. Setting this flag treats any [NA] as [A], and all of - message is sent. - These messages may still fail to SCL lo->hi timeout. - - Flags I2C_M_NO_RD_ACK - In a read message, master A/NA bit is skipped. +I2C_M_STOP: + Force a stop condition (P) after the message. Some I2C related protocols + like SCCB require that. Normally, you really don't want to get interrupted + between the messages of one transfer. diff --git a/Documentation/i2c/instantiating-devices b/Documentation/i2c/instantiating-devices index c70e7a7638d1..0d85ac1935b7 100644 --- a/Documentation/i2c/instantiating-devices +++ b/Documentation/i2c/instantiating-devices @@ -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 -------------------------------------------- |