No description
ec00968f08
In order to support doing bus operations on an I2C device that is
described in the devicetree there needs to be some linkage of the
device and the existing opaque I2C controller bus number.
This is provided in a similar fashion to the existing SMBUS operations
but modified to fit within the existing I2C infrastructure.
Variants of the existing I2C helper functions are provided that will
obtain the bus number that corresponds to this device by looking for
the SOC-provided I2C bus operation structure to provide a function
that will make that translation.
For example an SOC using a PCI I2C controller at 0:15.0 could use:
soc/intel/.../i2c.c:
static int i2c_dev_to_bus(struct device *dev)
{
if (dev->path.pci.devfn == PCI_DEVFN(0x15, 0))
return 0;
return -1;
}
static struct i2c_bus_operation i2c_bus_ops = {
.dev_to_bus = &i2c_dev_to_bus
}
static struct device_operations i2c_dev_ops = {
.ops_i2c_bus = &i2c_bus_ops
...
}
With an I2C device on that bus at address 0x1a described in the tree:
devicetree.cb:
device pci 15.0 on # I2C0
chip drivers/i2c/sample
device i2c 1a.0 on end
end
end
That driver can then do I2C transactions with the device object
without needing to know that the SOC-specific bus number that this
I2C device lives on is "0".
For example it could read a version value from register address 0
with a byte transaction:
drivers/i2c/sample/sample.c:
static void i2c_sample_enable(struct device *dev)
{
uint8_t ver;
if (!i2c_dev_readb(dev, 0x00, &ver))
printk(BIOS_INFO, "I2C %s version 0x02x\n", dev_path(dev), ver);
}
Change-Id: I6c41c8e0d10caabe01cc41da96382074de40e91e
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/15100
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
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| 3rdparty | ||
| Documentation | ||
| payloads | ||
| src | ||
| util | ||
| .clang-format | ||
| .gitignore | ||
| .gitmodules | ||
| .gitreview | ||
| COPYING | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc | ||
| README | ||
| toolchain.inc | ||
------------------------------------------------------------------------------- coreboot README ------------------------------------------------------------------------------- coreboot is a Free Software project aimed at replacing the proprietary BIOS (firmware) found in most computers. coreboot performs a little bit of hardware initialization and then executes additional boot logic, called a payload. With the separation of hardware initialization and later boot logic, coreboot can scale from specialized applications that run directly firmware, run operating systems in flash, load custom bootloaders, or implement firmware standards, like PC BIOS services or UEFI. This allows for systems to only include the features necessary in the target application, reducing the amount of code and flash space required. coreboot was formerly known as LinuxBIOS. Payloads -------- After the basic initialization of the hardware has been performed, any desired "payload" can be started by coreboot. See http://www.coreboot.org/Payloads for a list of supported payloads. Supported Hardware ------------------ coreboot supports a wide range of chipsets, devices, and mainboards. For details please consult: * http://www.coreboot.org/Supported_Motherboards * http://www.coreboot.org/Supported_Chipsets_and_Devices Build Requirements ------------------ * make * gcc / g++ Because Linux distribution compilers tend to use lots of patches. coreboot does lots of "unusual" things in its build system, some of which break due to those patches, sometimes by gcc aborting, sometimes - and that's worse - by generating broken object code. Two options: use our toolchain (eg. make crosstools-i386) or enable the ANY_TOOLCHAIN Kconfig option if you're feeling lucky (no support in this case). * iasl (for targets with ACPI support) Optional: * doxygen (for generating/viewing documentation) * gdb (for better debugging facilities on some targets) * ncurses (for 'make menuconfig' and 'make nconfig') * flex and bison (for regenerating parsers) Building coreboot ----------------- Please consult http://www.coreboot.org/Build_HOWTO for details. Testing coreboot Without Modifying Your Hardware ------------------------------------------------ If you want to test coreboot without any risks before you really decide to use it on your hardware, you can use the QEMU system emulator to run coreboot virtually in QEMU. Please see http://www.coreboot.org/QEMU for details. Website and Mailing List ------------------------ Further details on the project, a FAQ, many HOWTOs, news, development guidelines and more can be found on the coreboot website: http://www.coreboot.org You can contact us directly on the coreboot mailing list: http://www.coreboot.org/Mailinglist Copyright and License --------------------- The copyright on coreboot is owned by quite a large number of individual developers and companies. Please check the individual source files for details. coreboot is licensed under the terms of the GNU General Public License (GPL). Some files are licensed under the "GPL (version 2, or any later version)", and some files are licensed under the "GPL, version 2". For some parts, which were derived from other projects, other (GPL-compatible) licenses may apply. Please check the individual source files for details. This makes the resulting coreboot images licensed under the GPL, version 2.